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In a gasoline engine, the unswept in-cylinder residual gas and introduction of external EGR is one of the important means of controlling engine raw NOx emissions and improving part load fuel economy via reduction of pumping losses. Since the trapped in-cylinder Residual Gas Fraction (RGF, comprised of both internal, and external) significantly affects the combustion process, on-line diagnosis and monitoring of in-cylinder RGF is very important to the understanding of the in-cylinder dilution condition. This is critical during the combustion system development testing and calibration processes. However, on-line measurement of in-cylinder RGF is difficult and requires an expensive exhaust gas analyzer, making it impractical for every application. Other existing methods, based on measured intake and exhaust pressures (steady state or dynamic traces) to calculate gas mass flowrate across the cylinder ports, provide a fast and economical solution to this problem.

Accurate accounting for fresh charge (fuel and air) along with trapped RGF is essential for the subsequent thermodynamic analysis of combustion in gasoline engines as well as for on-line and real-time quantification as relevant to engine calibration and control. Cost and complexity of such techniques renders direct measurement of RGF impractical for running engines. In this paper, an empirically-based approach is proposed for on-line RGF, based on an existing semi-empirical model [1]. The model developed expands the range over which the semi-empirical model is valid and further improves its accuracy. The model was rigorously validated against a well correlated GT-POWER model as well as results from 1D gas exchange model [2]. Overall, using this model, RGF estimation error was within ∼1.5% for a wide range of engine operating conditions. The model will be implemented in Dyno development and calibration at Chrysler Group.

To achieve higher thermal efficiency for spark- ignition (SI) engines, advanced rapid combustion technology under high compression ratio is needed. The results of single-cylinder preliminary engine tests using E.U. commercial fuel at 96 RON show that the higher the compression ratio, the faster the combustion speed. Additional engine test and computations using S5R five-component surrogate gasoline with reliable chemistry under various temperature and pressure conditions implied that the autoignition assisted flame played significant role under higher compression ratio conditions, i.e., high temperature and pressure conditions, where apparent increases in laminar flame speeds compared to conventional combustion.

Charge motion is known to accelerate and stabilize combustion through its influence on turbulence intensity and flame propagation. The present work investigates the effect of charge motion generated by intake runner blockages on combustion characteristics and emissions under part-load conditions in SI engines. Firing experiments have been conducted on a DaimlerChrysler (DC) 2.4L 4-valve I4 engine, with spark range extending around the Maximum Brake Torque (MBT) timing. Three blockages with 20% open area are compared to the fully open baseline case under two operating conditions: 2.41 bar brake mean effective pressure (bmep) at 1600 rpm, and 0.78 bar bmep at 1200 rpm. The blocked areas are shaped to create different levels of swirl, tumble, and cross-tumble. Crank-angle resolved pressures have been acquired, including cylinders 1 and 4, intake runners 1 and 4 upstream and downstream of the blockage, and exhaust runners 1 and 4.

In the previous study of the authors, it was found that some benefits for the mixture preparation of DI gasoline engines can be offered by splitting the fuel injection, such as the phenomenon of high density liquid phase fuel piling up at the leading edge of the spray can be circumvented. In a further analysis, the vapor quantity in the “stable operating” range (equivalence ratio of vapor ϕv in a range of 0.7≤ϕv≤1.3) was significantly increased by the split injection compared to the single injection. In this work, the mechanism of the effect of the split injection on the mixture formation process was studied by combining the laser-sheet imaging, LIF-PIV and the LAS (Laser Absorption Scattering) technique. As a result, it is found that the spray-induced ambient air motion can help the formation of the more combustible mixture of the split injection whereas it played a minus role of diluting the spray by the single injection.

Coating the heat insulation materials on the combustion chamber walls is one of the solutions to reduce the cooling loss of internal combustion engines. In order to examine the coatings, the evaluation of the heat transfer coefficient and the analysis of the heat transfer phenomena on the heat insulated walls are important. Firstly, the highly-responsive wall temperature sensor is developed, and the instantaneous wall heat flux is measured to evaluate the heat transfer coefficient on the heat insulated walls. The results show that the Nusselt number on the heat insulated walls is less influenced by the Reynolds number variation than that on the metal walls. Secondly, the high speed µ-PIV is employed to analyze the various turbulent flow characteristics. The results show that the turbulent dissipation on the heat insulated walls is smaller than that on the metal walls.

Heat loss is more critical for the thermal efficiency improvement in small size diesel engines than large-size diesel engines. More than half of total heat energy in the internal-combustion engine is lost by cooling through the cylinder walls to the atmosphere and the exhaust gas. Therefore, the new combustion concept is needed to reduce losses in the cylinder wall. In a Direct Injection (DI) diesel engine, the spray behavior, including spray-wall impingement has an important role in the combustion development to reduce heat loss. The aim of this study is to understand the mechanism of the heat transfer from the spray and flame to the impinging wall. Experiments were performed in a constant volume vessel (CVV) at high pressures and high temperatures. Fuel was injected using a single-hole injector with a 0.133 mm diameter nozzle. Under these conditions, spray evaporates, then burns near the wall. Spray/flame behavior was investigated with a high-speed video camera.

The combustion process, emission formation and the resulting engine performance in a diesel engine are well known to be governed mainly by spray behaviors and the consequent mixture formation quality. One of the most important factors that affect the spray development is the nozzle configuration. Originally, single-hole diesel injector is usually applied in fundamental research to provide insights into the spray characteristics. However, the spray emerging from a realistic multi-hole injector approaches the practical engine operation situation better. Meanwhile, previous research has shown that the reduced nozzle hole diameter is effective for preparing more uniform mixture. In the current paper, a study about the effects of nozzle configuration and hole diameter on the internal flow and spray properties was conducted in conjunction with a series of experimental and computational methods.

This study attempts to develop a correlation between an airflow motion number, combustion burn rates, and initial flame kernel development. To accomplish this task, several motion plates were evaluated on a flowbench in order to calculate a motion number that would represent the dynamic motion in the combustion chamber. Afterwards, the plates were tested on a spark ignited engine at several part throttle conditions while gathering cylinder pressure measurements. These cylinder pressure measurements would then yield the combustion burn rates for each plate. In addition to the combustion measurements, the flame kernel growth, velocity and direction of the flame kernel were measured using an AVL Visio-flame. Finally, the data was evaluated and an attempt to correlate the motion number of the plates to the different measurements for describing combustion was made.

A mixed time-scale subgrid large eddy simulation was used to simulate mixture formation, combustion and soot formation under the influence of turbulence during diesel engine combustion. To account for the effects of engine wall heat transfer on combustion, the KIVA code's standard wall model was replaced to accommodate more realistic boundary conditions. This were carried out by implementing the non-isothermal wall model of Angelberger et al. with modifications and incorporating the log law from Pope's method to account for the wall surface roughness. Soot and NOx emissions predicted with the new model are compared to experimental data acquired under various EGR conditions.

The newly developed rotary engine has achieved major progress in high performance, improved fuel economy and clean exhaust gas by innovative action. The engine of the next generation is named RENESIS, which stands for “The RE (Rotary Engine)'s GENESIS” or the rotary engine for the new millennium. The peripheral exhaust port of the previous rotary engine is replaced by a side exhaust port system in the RENESIS. This allows for an increase in the intake port area, thus producing higher power. Exhaust opening timing is retarded to improve thermal efficiency. The side exhaust port also allows reducing the internal EGR, stabilizing the combustion at idling. The improved thermal efficiency and the stabilized idle combustion result in higher fuel economy. In addition, the side exhaust port allows a reduction of the HC mass, realizing reduced exhaust gas emission.

In this paper, a simplified prediction model for aiming to design an engine control system of Homogeneous Charge Compression Ignition (HCCI) engine has been developed. Developed HCCI engine model is for rebreathing concept and employs the discretized cycle concept to realize fast calculation speed. The ignition timings are predicted by Livengood-Wu integration combined with a function of ignition delay and the combustion durations are predicted from supplied fuel mass quantity. Maximum pressure and its phase are compared to experiments. In addition, for designing an HCCI engine, the models to predict appropriate operation conditions are considered.

Control of self-ignition timing in a HCCI engine is still a major technical issue. Recently, the application of a non-equilibrium plasma using repetitively discharge has been proposed as the promising technology. However, non-equilibrium plasma reaction in higher hydrocarbon fuel mixture is very complicated. Hence, there have been few calculation reports considering a series of reactions from non-equilibrium plasma production to high temperature oxidation process. In this study, 0-dimensional numerical simulation model was developed in which both reactions of plasma chemistry and high temperature oxidation combustion was taken into account simultaneously. In addition, an ODEs solver has been applied for the reduction of calculation time in the simulation. By comparing calculation results with experiment such as self-ignition timing, the validity of the developed numerical model has been evaluated.

The thermal efficiency of a three-rotor rotary engine (RE) was improved by a reduction in the pumping losses. These pumping losses were reduced by using a new port mechanism. The port mechanism utilized was an indirect recirculation type of late intake port closing. It was equipped with a recirculation chamber outside of the housings. This chamber interconnected the recirculation ports within each housing. This port mechanism yielded three main benefits 1. A Considerable reduction in the pumping losses. 2. A uniformly distributed air-fuel mixture in each housing. 3. A limited amount of residual gas in the housing. This residual gas was under specific pulsations by the recirculation chamber thus preventing deterioration in combustion under light loads. The above phenomena were clarified by experiments and simulations. The possibility of a reduction in exhaust emissions was also investigated.

Automobiles will have to be applied strict regulations such as Euro7 against PM, HC, CO. The generation of these components are related to fuel deposition to the wall surface of the combustion chamber. Therefore, the fuel injection model of engine combustion CFD requires accurate prediction about the deposition and vaporization of fuel on the combustion chamber. In this study, multiphase flow numerical analysis that simulates fuel behavior on the wall surface was conducted first. Then, two model formulae about the contact area and the heat flux of a liquid film was constructed based on the result of multiphase flow numerical analysis method. Finally, the new film heat transfer model was constructed from these model formulae. In addition, it was confirmed that new heat transfer model can predict the liquid film temperature obtained by multiphase flow numerical analysis method accurately.

The reduced chemical reaction scheme which can take the effect of major fuel components on auto ignition timing into account has been developed. This reaction scheme was based on the reduced reaction mechanism for the primary reference fuels (PRF) proposed by Tsurushima [1] with 33 species and 38 reactions. Some pre-exponential factors were modified by using Particle Swarm Optimization to match the ignition delay time versus reciprocal temperature which was calculated by the detailed scheme with 2,301 species and 11,116 elementary chemical reactions. The result using the present reaction scheme shows good agreements with that using the detailed scheme for the effects of EGR, fuel components, and radical species on the ignition timing under homogeneous charge compression ignition combustion (HCCI) conditions.

A new nitrogen oxide (NOx) reduction concept is suggested. A strong vertical vortex generated within the combustion bowl can mix hot burned gas into the cold excess air at the center of the combustion-bowl. This makes the burned gas cool rapidly. Therefore, it is possible to reduce NOx, which would be produced if the burned gas remained hot. In this paper the effect was verified with a 3D-CFD analysis of spray, air, combustion gas, and thermal efficiency as well as experiments on a 4-cylinder 2.0-liter direct injection diesel engine. The results confirmed that the vertical vortex was able to be strengthened with the change of spray characteristics and the combustion bowl shapes. This strengthened vertical vortex was able to reduce NOx by approximately 20% without making smoke and thermal-efficiency worse. Above results proved the effectiveness of this method.

This investigation evaluated different pressure transducers in one cylinder to examine the combustion measurement differences between them simultaneously. There were a total of eleven transducers ranging in both diameter and type of transducer (piezo-electric, piezoresistive, and optical). Furthermore, the sensors differed in the methodology for minimizing signal distortion due to temperature. This methodology could take the form of various size mounting passages, heat shields, watercooling or heat transfer paths. To evaluate the sensors, different engine operating conditions were conducted, focusing at full load and low speeds. Other hardware configurations of the same engine family were used to exaggerate the combustion environment, specifically a tumble-motion plate and turbocharging.

The method described in this paper has been proposed to analyze the heat balance of diesel combustion from engine measurement data considering the heterogeneity of this type of combustion with use of a two-zone model composed of unburned and burned zones. This method is intended for practical application to an engine bench test during an engine development process and is characterized by the following features: A representative excess air ratio of the burned zone is set and assumed to be constant throughout the combustion period, and the ratio is estimated from NOx emission amount. The authors performed heat balance analyses on engine measurement data using the proposed method and made a comparison with the results of analyses that assumed a combustion chamber to be one homogenous zone.

As a technology to reduce the heat loss of engines, heat insulation coating to the surface of combustion chamber has been received a lot of attention. In order to maximize the thermal efficiency improvements by the technology, it is important to clarify the location where heat insulation coating can reduce heat loss more effectively, considering the impact on abnormal combustion etc. In this study, transient behavior of wall heat flux distribution on the piston was analyzed using 3D Computational Fluid Dynamics (CFD) for three combustion modes (spark ignition combustion (SI), homogenous charge compression Ignition (HCCI) and spark controlled compression ignition (SPCCI)).