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Exhaust after-treatment (EAT) systems on automotive vehicles cannot perform effectively at low loads due to low exhaust temperatures (Texhaust < 250oC). Con-ventional late intake valve closure (LIVC) technique - a proven method to im-prove diesel exhaust temperatures - generally requires the modulation of the whole valve lift profile. However, an alternative method - boot-shaped LIVC - only needs partial lift form modulation and can rise exhaust temperatures signif-icantly. Therefore, this study attempts to demonstrate that boot-shaped LIVC can be an alternative solution to improve exhaust temperatures above 250oC at low-loaded operations of automotive vehicles.A 1-D engine simulation program is used to model the diesel engine system operating at 1200 RPM engine speed and at 2.5 bar brake mean effective pres-sure (BMEP) engine load. Boot-shaped LIVC is achieved via keeping the valve lift constant (at 4.0 mm) for a while during closure and then closing it at different closure angles. The method results in up to 55oC exhaust temperature rise through reduced in-cylinder airflow and thus, is adequate to keep EAT system above 250oC at low loads. The longer the boot is kept during closure, the lower the air-to-fuel ratio is reduced and the higher the exhaust temperature flows at turbine exit. Similar to conventional LIVC, boot-shaped LIVC improves fuel con-sumption as pumping losses are decreased in the system. Despite aforementioned improvements, EAT warm-up is affected negatively due to the significant drop-off on exhaust mass flow rates. The need to modify only some parts of the lift profile is a technical advantage and can reduce production costs.

A comprehensive analysis of the intake valve opening duration (IVOD) effects on the performance of an Atkinson cycle engine is conducted in this work using numerical simulation and experimental validation. Through one-dimensional simulation, the relationship between the range of IVOD and the compression ratios is firstly investigated under the constraint of compression pressure. Two representative IVOD, 295 and 314°CA, are then respectively applied to the performance simulation and experiment of a practical Atkinson cycle engine. The simulation shows the combination of a late intake valve opening timing (IVO) angle and a late exhaust valve opening timing (EVO) angle is profitable for improving the fuel economy under part load operating conditions (i.e. 2000 rpm@2 bar and 3000 rpm@3 bar). The experimental results present the Atkinson cycle engine under both IVOD scenarios considerably improves the brake specific fuel consumption (BSFC) and reduces the pumping mean effective pressure (PMEP) compared to those of the original Otto cycle engine. Meanwhile, the comparison between two IVOD scenarios show that the shorter IVOD leads to an improvement of indicated thermal efficiency, especially at lower load. Considering fuel economy, a shorter IVOD is more favorable at part load for the Atkinson cycle engine. Two main contributions of this work are to numerically quantify the IVOD range for the Atkinson cycle engine under part load, and to experimentally validate the effectiveness of simulation. The findings of this work are expected to support the design of Atkinson cycle engines and provide a guideline of IVOD optimization under part load.

This paper experimentally and numerically studied the effects of fuel combination and intake valve opening (IVO) timing on combustion and emissions of an n-heptane and gasoline dual-fuel homogeneous charge compression ignition (HCCI) engine. By changing the gasoline fraction (GF) from 0.1 to 0.5 and the IVO timing from −15°CA ATDC to 35°CA ATDC, the in-cylinder pressure traces, heat release behaviors, and HC and CO emissions were investigated. The results showed that both the increased GF and the retarded IVO timing delay the combustion phasing, lengthen the combustion duration, and decrease the peak heat release rate and the maximum average combustion temperature, whereas the IVO timing has a more obvious influence on combustion than GF. HC and CO emissions are decreased with reduced GF, advanced IVO timing and increased operational load.

The article provides the study on causes of damage to ICE intake valves, in the course of which the intake valve heads have been overheated and deformed as a result of material creep. On the example of the failure detected in the analysed engine, it has been established that the traditionally known reasons such as the combustion process failure cannot cause the damage described. For the purpose of determining the real causes of damage to the intake valves the authors simulated the thermal state of the intake valve in the heatingcooling conditions with the impact of gas in the cylinder and the impact of air in the intake pipe as well as the contact heat exchange with the seat with regard to thermal conductivity along the stem. The calculations have shown that with the increase of rotation frequency the failure of the control system that causes the engine to run at high rotation frequencies with a small intake valve lift leads to the temperature increase higher than it is recommended for the materials used, which causes the described overheating. Based on the conducted research the authors have developed recommendations for improving the reliability of the intake valves performance in the ICEs with variable valve timing.

In this research, intake runner length, and valve timing are varied individually and simultaneously over a range of values to capitalize the induction pressure waves to boost volumetric efficiency. 1-D model of the stock engine built in Ricardo Wave software is validated with 90% accuracy against experimental test results. The volumetric efficiency of the engine is boosted by an average of 3.2% over the speed range of the engine when infinitely variable runner lengths are used. When only two variations in runner length are used, the volumetric efficiency has boosted by around 1.4% on average. On the other hand, when infinitely variable valve timings along with two variations in runner lengths are used, the volumetric efficiency has boosted by an average of 7.78 %. Due to the existence of two different runner lengths, the span of variations required in valve timing is reduced further optimizing the volumetric efficiency. However, to ensure feasibility of the design, manufacturing, assembly and operation, it is better to use only two valve timings. The co-presence of only two different runner lengths and two different valve-opening timings, the average boost of 5.40 % in volumetric efficiency throughout the operating speed range of the engine is encountered Refereed/Peer-reviewed

The SI engines in passenger cars run in the partial-load conditions in the most time especially in the urban driving cycles; thus it is particularly important to improve the partial-load fuel economy. Cylinder deactivation (CDA) and variable valve timing (VVT) could be applied to improve the fuel economy in the middle to low load region. Current CDA technologies are realized by deactivating all intake and exhaust valves (CDAV) of the inactive cylinders with special mechanisms increasing system cost and complexity. An innovative CDA method is proposed for 4-cylinder SI engines through double intake manifolds (CDAM). A novel load control strategy combining the CDAM and VVT along with late intake valve closure (LIVC) has been investigated. The results show that the pumping loss decreases by 58.9–65.6% and 24.5–35.3%; and the fuel economy improves by 5.5–17.6% and 3.1–9.2% in the CDA mode at 2000 rpm and 4000 rpm, respectively. The fuel economy in the full-cylinder mode also improves by 0.68–2.95% because of the application of the double intake manifolds. The strategy is more effective in the low speed range and more suitable for the urban driving cycles. Although a less fuel economy improvement than the CDAV method, the CDAM method can be realized with less cost and complexity.

This work is aimed at improving the performance of the air-powered rotary engine. A dynamic simulation model which includes an eccentric motion and rotary valve movement was established by our particle image velocimetry (PIV) experimental data. Then the power and specific steam consumption (SSC) was evaluated. The pressure distribution in the chamber was obtained which was difficult to obtain through experiment. Simulation results showed that for the work process and pressure distribution, the intake valve timing mainly affected the intake expansion stage (A2) and pure expansion stage (B). Due to this, a relatively low pressure was distributed in the middle of the chamber and this was beneficial to the intake and work processes. The exhaust valve timing mainly affected the exhaust stage (C) and initial intake stage (A1). Therefore, a relatively high pressure which was distributed in the middle-rear of the chamber was beneficial to the exhaust processes. For the power and SSC, the power increased initially then decreased and the SSC decreased with the increase of intake advance angle respectively. Both the power and the SSC increased with the increase of intake duration angle. The power increased while the SSC decreased with the increase of exhaust advance angle. The power increased and the SSC decreased initially then increased with the increase of exhaust duration angle. The preferred parameters were found to be 30° CA, 240° CA, 30° CA, and 280° CA. These improved parameters had a 2.7% increase in the power and also a 2.4% decrease in the SSC. © 2017 American Institute of Chemical Engineers Environ Prog, 2017

The optimization design of engine is always one of the top concerns in motorcycle industry. In this paper, effective torque and fuel consumption ratio are defined as the performance evaluation indexes of engine, while air-fuel ratio, intake valve timing angle, exhaust valve timing angel, pressure, and temperature are defined as input variables. With the application of DOE methodology, a full factorial DOE is conducted to estimate the regression model and identify the statistical significant factors. And then, with the selection of additional experimental points, RSM is introduced to construct the precise regression model between input variables and performance indexes. Based on that, an optimum solution that can satisfy both performance requirements are brought forward and testified.

An experimental study has been conducted to explore the effects of five different valve strategies, including three intake valve closure (IVC) timing strategies and two rebreathing strategies (i.e., second opening of the intake/exhaust valves during the exhaust/intake processes, called 2IVO and 2EVO) on the combustion and emission characteristics at various low loads (1–5 bar gross indicated mean effective pressure, IMEP g ) on a heavy-duty diesel engine. Then proper valve strategies to achieve clean combustion (Engine-out emission: NO x ~0.4 g/kW-hr, Smoke x emissions within low levels, the externally cooled exhaust gas recirculation (Ex-EGR) was used and combined with three IVC strategies in this study, while internal EGR (In-EGR) was used with 2IVO and 2EVO strategies. The results show that low NO x emissions can be achieved for these valve strategies with high In-EGR or Ex-EGR. However, the differences among various valve strategies on other emissions (CO, HC and Smoke) and combustion characteristics are sensitive to engine loads. Improved combustion and emissions can be achieved with rebreathing strategies at low loads (1–2 bar IMEP g ), however, higher Smoke emissions and lower thermal efficiency are observed at higher loads. The lowest Smoke emissions can be obtained with the late IVC strategy, but at the same time with high CO and HC emissions, especially at lower loads. The suggestion is to use the rebreathing valve strategies at lower engine load from 1 to 2 bar IMEP g and then change to the standard and late IVC strategies at higher loads.

Electromagnetic intake valve train (EMIV) is capable of regulating the intake valve control parameters such as intake phase, valve lift and transitional time at any given operational condition, which provide an effective way to improve the performance of engine. So the engine model was established to research the intake quantity influenced by intake valve variables such as intake phase, valve lift, transitional time and single/double mode, then the maximum of intake charging and the related control parameters under different engine speeds were obtained; combined with power consumption of the EMIVs and pumping loss, the control parameters with higher efficiency were obtained to satisfy the intake quantity. The results show that by EMIVs, the intake changing of the engine can be significantly improved, especially at lower engine speed which the increase can be reached by 18.3%; what’s more, by optimized valve control parameters, the power consumption in the air charging process can be reduced under the same intake charging, for example, the power consumption of single valve model will decrease by 35.9% compared with the double valve model at 2000 rpm.

Natural gas proposed to replace liquid fossil fuels in high-speed engines, which were considered a cleaner fuel, lower emissions, and more efficient. However, natural gas had several disadvantages. Natural gas was thought to cause abnormal combustion and methane slip phenomenon as the primary fuel in the dual-fuel engines. This experiment has investigated the natural gas injection on a dual-fuel engine. This study aims to minimize the appearance of abnormal combustion phenomena, such as knocking, misfiring, and pre-ignition, while reducing methane slip. Investigations were carried out to see how injection timing, duration, and natural gas intake pressure on combustion performance at low load. This study concluded that the injection timing should be reversed near the intake valve closure by adjusting the injection duration or reducing gas pressure. It affects to reduce the abnormal combustion and methane slip in low load. The injection timing effect was more dominant on combustion operations than the duration injection and intake gas pressure setting to reduce methane slip and avoid abnormal combustion in diesel – natural gas dual-fuel engine.

A common approach of high efficiency engines is to utilize high compression with late intake valve closing (LIVC) to realize an over-expanded cycle. A multi-link cranktrain can also realize an over-expanded cycle with the same geometric intake displacement as a baseline engine while extending the expansion stroke. These two types of over-expanded cycle engines and a baseline engine are investigated and compared in this simulation study. The baseline engine model is calibrated based on the experimental results from a four-cylinder, boosted, spark-ignited engine with compression ratio (CR) of 10.5:1. The CR of high compression ratio engine and multi-link over-expanded engine is 13.0:1 and 10.5:1, respectively. The over-expansion ratio of multi-link engine is 1.5. These three engines were optimized and investigated at three conditions: 1300 rpm 330 kPa net IMEPnet, 1500 rpm 1300 kPa IMEPnet, and 2500 rpm 1000 kPa IMEPnet. At 1300 rpm 330 kPa IMEPnet, multi-link over-expanded engine and high compression engine both used LIVC. With LIVC, the net indicated efficiency of the high compression engine and multi-link engine were improved by 5.2% and 2.4% (relative), respectively, compared to the same engine without LIVC. Multi-link over-expanded engine benefited from its lower knock propensity and over-expansion at medium to high load conditions. At 1500 rpm 1300 kPa IMEPnet, the net indicated efficiency of the multi-link engine was 13.7% and 14.2% (relative) higher than the high compression engine and baseline engine, respectively. At the peak brake efficiency condition of the high compression engine, the net indicated efficiency of multi-link engine was 8.6% (relative) higher than the high compression engine.

The camless electromagnetic valve train (EMVT), as a fully flexible variable valve train, has enormous potential for improving engine performances. In this paper, a new valve strategy based on the electromagnetic intake valve train (EMIV) is proposed to achieve variable cylinder deactivation (VCD) on a four-cylinder gasoline engine. The 1D engine model was constructed in GT-Power according to test data. In order to analyze the VCD operation with the proposed valve strategy, the 1D model was validated using a 3D code. The effects of the proposed valve strategy were investigated from the perspective of energy loss of the transition period, the mass fraction of oxygen in the exhaust pipe, and the minimum in-cylinder pressure of the active cycle. On the premise of avoiding high exhaust oxygen and oil suction, the intake valve timing can be determined with the variation features of energy losses. It was found that at 1200 and 1600 rpm, fuel economy was improved by 12.5&ndash, 16.6% and 9.7&ndash, 14.6%, respectively, under VCD in conjunction with the early intake valve closing (EIVC) strategy when the brake mean effective pressure (BMEP) ranged from 0.3 MPa to 0.2 MPa.

The current research of compressed air engine (CAE) mainly focused on simulations and system integrations. However, energy efficiency and output torque of the CAE is limited, which restricts its application and popularization. In this paper, the working principles of CAE are briefly introduced. To set a foundation for the study on the optimization of the CAE, the basic mathematical model of working processes is set up. A pressure-compensated valve which can reduce the inertia force of the valve is proposed. To verify the mathematical model, the prototype with the newly designed pressure-compensated intake valve is built and the experiment is carried out, simulation and experimental results of the CAE are conducted, and pressures inside the cylinder and output torque of the CAE are obtained. Orthogonal design and grey relation analysis are utilized to optimize structural parameters. The experimental and optimized results show that, first of all, pressure inside the cylinder has the same changing tendency in both simulation curve and experimental curve. Secondly, the highest average output torque is obtained at the highest intake pressure and the lowest rotate speed. Thirdly, the optimization of the single-cylinder CAE can improve the working efficiency from an original 21.95% to 50.1%, an overall increase of 28.15%, and the average output torque increases also increases from 22.047 5 N • m to 22.439 N • m. This research designs a single-cylinder CAE with pressure-compensated intake valve, and proposes a structural parameters design method which improves the single-cylinder CAE performance.

To improve the energy efficiency and output power of the piston compressed air engine (CAE), a mathematical model of its working process was set up. With the use of the MATLAB/Simulink software for simulation, the influences of the bore-to-stroke ratio, intake pressure and valve lift on the performance of the engine were obtained for the analysis of the energy efficiency and the output power. Moreover, to optimize the energy efficiency of the engine with the given output power, an improved NSGA-II was introduced, and a series of optimization intake pressures and valve lifts was obtained. When the output power value is about 2 kW, the intake pressure and the intake valve lift can be set to 1.99 MPa and 9.99 mm, the energy efficiency is highest: 31.17%. Finally, that the improved NSGA-II is superior to NSGA-II in proximity and diversity has been proved. This research can be referred in the optimization of the piston CAE and provides a method for the energy efficiency optimization study. Kurjenje fosilnih goriv je eden glavnih vzrokov resnih okoljskih problemov, kot so učinek tople grede, tanjšanje ozonske plasti in smog. V članku je predstavljena nova vrsta pogonske opreme, ki bi lahko pomagala pri odpravljanju teh problemov. Batni motor (CAE) poganja stisnjen zrak, ki ga je mogoče pridobiti z uporabo obnovljivih virov, kot so sončna svetloba, veter in bibavica. Batni motorji CAE so okolju prijazna oprema in bi jih lahko vgrajevali v vozila prihodnosti, njihov razvoj pa je začasno zavrla nizka energetska učinkovitost.

A combination of downsizing, highly boosting and direct injection (DI) is an effective way to improve fuel economy of gasoline engines without the penalties of reduced torque or power output. At high loads, however, knock problem becomes severer when increasing the intake boosting. As a compromise, geometric compression ratio (CR) is usually reduced to mitigate knock, and the improvement of fuel economy is discounted. Application of Miller cycle, which can be realized by either early or late intake valve closing (EIVC or LIVC), has the potential to reduce the effective CR and suppress knock. In this paper, the effects of EIVC and LIVC on the fuel economy of a boosted DI gasoline production engine reformed with a geometric CR of 12.0 are experimentally compared at low and high loads. Compared to the original production engine with CR 9.3, at the high load operation, the brake specific fuel consumption (BSFC) is improved by 4.7% with CR12.0 and LIVC, while the effect of EIVC on improving BSFC is negligibly small. At the low load operation, combined with CR12.0, LIVC and EIVC improve the fuel economy by 6.8% and 7.4%, respectively, compared to the production engine. The mechanism behind the effects of LIVC and EIVC on improving the fuel economy is discussed. These results will be a valuable reference for engine designers and researchers.

In this study, 2 different valve-angle engines, one is wide and the other is narrow, were prepared for investigating the effects of the angle on the combustion. For this purpose, the part load performances were evaluated and the pressures were measured for combustion analysis at an engine bench under 5 different operating conditions, varying the compression ratio. The results show that the combustion proceeds so faster in the small IVA engine that its MBT timings are retarded considerably compared with that of large one and result in lower NOx emission level; however, unburned HC is higher because of its geometrical feature. In addition, there is no substantial difference between 2 IVA engines in the timings of combustion initiation and completion as a crank-angle-position-base in spite of the considerable difference of spark timing, on the other hands, the ignition delay of the small IVA is shorter than that of large one. Also the phenomena that the flame propagation is faster and the instant heat release rate is more concentrated and higher in the small were observed. Also, the burn duration of small one is shorter and the combustion process is more accelerated up to the mid-combustion stage; however, the process of large one is faster as the combustion approaches the last stage and the differences of combustion duration reduce as the compression ratio increases. Finally, the engine runs more stable when the IVA is small without any exception because of its rapid burn at the initial combustion stage.

International audience; Reducing fuel consumption is a prime objective in the automotive industry in order to meet regulatory and customer demands. Variable valve actuation offers many opportunities for improving the spark ignition engine’s performance in areas such as fuel economy and pollutant emissions. Our studies revealed that the ability to control maximum intake valve lift does indeed offer the ability to control intake air mass, but also has the added benefit that it improves the fuel-air mixing process thanks to an increased turbulence, caused by the increased intake flow velocity. This is particularly important at idle and low part loads when low maximum lifts are to be used for improving the fuel economy or for achieving the required power. The paper focuses on the experimental results obtained when approaching idle operation with different intake valve laws. Results indicating the potential of using low intake valve lift for fuel economy and cyclic dispersion improvement are presented in this paper.

A diesel engine used in a truck had a trouble when servicing. Inspection indicated that four exhaust and intake valve springs and two exhaust and intake valves were fractured. Fractographic studies indicated that fatigue fracture is the main failure mechanism for all of the four valve springs. Under the action of the maximum normal stress, the fatigue crack initiated in the spring wire of coil 1.3-1.5 from the upper end of the spring. This region is also the most damaged location by contact friction wear. The fracture of the intake and exhaust valve stems also suggests fatigue failure probably as a result of the failure of the associated valve springs.

Une analyse numerique du processus d'evolution de l'ecoulement dans le plan axial d'un cylindre d'un moteur a deux soupapes et quatre temps pendant la course d'admission est effectuee en utilisant une methode d'elements-finis pour un probleme a frontieres mobiles. Le domaine de calcul, a geometrie variable, inclut simultanement le conduit d'admission, la region de la soupape et la chambre de combustion. Le mouvement des interfaces entre le fluide, le piston et la soupape a ete considere. La methode Lagrangienne Eulerienne Arbitraire (ALE) a ete utilisee pour decrire les champs aerodynamique et thermique. Deux modeles d'interpolation des vitesses de maillage ont ete adoptes : l'un est rattache au mouvement du piston et l'autre a celui de la soupape. Le processus d'evolution et d'etablissement des diverses structures tourbillonnaires et du champ thermique dans le plan axial du cylindre, caracterise par une chambre hemispherique et des soupapes laterales, est presente. Cette etude a montre que la modelisation adoptee conduit a une simulation numerique avec une precision raisonnable en comparaison avec les resultats experimentaux publies recemment.

The feed forward controller of a camless internal combustion engine is modeled by inverting a multi-input multi-output feed forward artificial neural network (ANN) model of the engine. The engine outputs, pumping loss and cylinder air charge, are related to the inputs, intake valve lift and closing timing, by the artificial neural network model, which is trained with historical input–output data. The controller selects the intake valve lift and closing timing that will mimimize the pumping loss and achieve engine torque tracking. Lower pumping loss means better fuel economy, whereas engine torque tracking gurantees the driver’s torque demand. The inversion of the ANN is performed with the complex method constrained optimization. How the camless engine inverse controller can be augmented with adaptive techniques to maintain accuracy even when the engine parts degrade is discussed. The simulation results demonstrate the effectiveness of the developed camless engine controller.

Residual-effected homogeneous charge compression ignition (HCCI) was investigated using a single-cylinder research engine equipped with fully-flexible variable valve actuation. Operation at elevated compression ratios was explored to determine its effect on efficiency. Results showed that efficiency is decreased significantly by advanced phasing owing to increased thermal losses. However, if combustion phasing is held fixed, elevated compression ratio operation showed little effect on efficiency. Further experiments explored the use of IVC time as a control parameter at the elevated compression ratio. Tests were conducted to determine if an efficiency benefit could be realized from increasing the compression ratio and delaying IVC to increase the extent of expansion relative to compression. No significant change in efficiency was observed, although variation in IVC timing offered significant control authority. Delayed IVC was used in conjunction with variable IVO to control independently load and phasing of HCCI at the elevated compression ratio. Tests were also conducted to assess the significance of the measured exhaust temperature on HCCI phasing. EVO was introduced as a third control parameter, along with IVO and IVC, to control independently initial mixture composition, compression work, and exhaust temperature. Results indicated that the measured exhaust temperature was not a good indicator of HCCI phasing and suggested the stabilizing role of heat transfer to the reinducted exhaust gases. Results also suggested a set of control parameters that achieve the full range of HCCI operation with minimal degrees of freedom.

Fatigue design of components subjected to cyclic loading requires special testing methods, component related material data and an appropriate safety concept. The following contribution presents a newly developed methodology for the fatigue design and testing of highly loaded ceramic components. This methodology is verified by laboratory and in-service testing of Si 3 N 4 intake and exhaust valves.

A new design is proposed for the intake valve of a gas distributor. The new design improves the heat transfer.

A Model S195 (8.8 kW) single cylinder was used in this study to determine the effect of four operational parameters, i. e. intake valve close angle, exhaust valve open angle, fuel delivery angle and fuel injection pressure on noise. Single factor and multi-factor quadratic regressive orthogonal methods were adopted in the experiments to find the relationship between the four parameters and noise. By means of optimization technique, the optimum operational parameters for two working conditions of the engine were selected and the test results showed that optimum adjustment could reduce noise by 2–4 dB.

The effects of gasoline composition doped with a trace amount of used engine oil on the formation of simulated intake valve deposit have been investigated. Studies were performed using a bench top simulator. Oxygenated gasoline has been found to exhibit a high deposit-forming tendency. In addition to the amount, the nature of the deposit formed also depends on the type of fuel used. For oxygenated fuel, a dry carbonaceous deposit is usually formed instead of the polymeric deposit that is commonly obtained from non-oxygenated fuel.

The degradation of engine oil and its influence on the formation of intake valve deposits is being discussed in this paper. Degraded samples of oil were prepared using a stationary engine testbed while deposition studies were performed using a bench top simulator. The degree of degradation, as indicated by the amount of polymeric, oxidized and oxidative products, increases as the engine oil is used over a period of time. The rate of degradation, however, varies depending on the quality of base oil and the type of additives used. It was observed that the degraded oil played an important role in the formation of inlet valve deposits.

A solenoid-drive type in-cylinder gas injection system was designed and constructed. The injection system was installed on a single cylinder research engine, and the engine performance and the emission of nitric oxide were measured with variation of the fuel-air equivalence ratio and the spark timing. The performance and emission characteristics of the in-cylinder injection type engine were compared with those of the intake port injection type engine. In the case of the in-cylinder injection type, hydrogen is injected after the intake valve closes, so the engine can be operated without flash-back and the loss of volumetric efficiency. The most distinct differences between the intake port injection type and the in-cylinder injection type are the enhanced volumetric efficiency of the in-cylinder injection type at high load, the high engine output and the high level of NO emissions at stoichiometry.

February 2006 32:1 s you are standing by the ambulance bay, how A often do you notice that the engine(s) of one or several ambulances are idling while patients are being delivered? How many times have you cleared your throat, coughed, sneezed, and discussed the noxious fumes with your co-workers? If you are like so many of us, you assume that any consequences of breathing these fumes will be short lived and relatively benign, but that was not the case for one career emergency nurse who worked in an emergency department located in a New England suburb. This woman was an ED nurse educator with a background of 15 years of ED staff nursing when her hospital’s busy emergency department underwent reconstruction and renovation. The ambulance bay was suddenly smaller, and the fumes from ambulances became more concentrated. Before the renovation, this nurse had noticed that she was occasionally hoarse when she was at work, but she also observed that the hoarseness resolved quickly once she left the emergency department. However, once the emergency department moved to its new location, she noticed immediately that she could actually smell the fumes in the emergency department when ambulances were idling in the bay. A new vent system, with an intake valve placed right in the ambulance bay, actually took in the air from the bay, exhaust fumes and all, and disseminated the ‘‘fresh air’’ throughout the emergency department. Initially this nurse suffered respiratory problems, but those problems quickly progressed to neurologic manifestations: She tripped easily, became forgetful, and her speech took on a slow, halting cadence. Once she was relocated from the emergency department, her symptoms diminished somewhat, but even now, several years later, she is still plagued by some neurologic sequelae. Initially she was allowed to work on ED policies

Vibration signature analysis (VSA) is one of many technologies for condition monitoring (CM) and diagnosis of reciprocating and rotating machines such as internal combustion engines (ICEs) valve train. CM practices have generally led to improved machine availability and decreased maintenance costs. The cylinder head with overhead valve (OHV) of diesel ICE was used as the experimental set–up. The objective of this paper is focused specifically on the effects on VSA of two types of valve train artificial fault conditions (abnormal clearance of intake valve and crack of the exhaust valve head). The experimental results and analysis showed that surface vibration signature is an effective method to detect damage and the type of damage in valves in both the time and frequency domains. The results indicated the proposed statistical technique is effective in fault diagnosis for experimental cases, and this is considered to be a unique approach to condition monitoring of valve performance.