Suzuki Takashi

The amount of air into IC engine's cylinders is affected by the heat transfer at the intake system, which is changed by the development of thermal boundary layer, the opening and closing of intake valve, and so forth. Our previous study developed the empirical equation for the intake manifold model assuming as the cycle-averaged quasi-steady state heat transfer. On the other hand, the present study also improved the newly empirical equation with the quasi-steady state heat transfer for the intake manifold of the actual IC engine. Consequently, the Nusselt number used in the newly empirical equation was expressed by using the Reynolds number, the Gratez number and the Strouhal number, which represents the effects of the intake air gas flow rate, the development of thermal boundary layer and the engine speed, respectively. In addition, the outlet air temperature at the intake port was estimated with the accuracy of maximum error of 5.6%, which was improved in comparison with the results obtained from the Colburn equation.

Prediction of ignition timing through model-based control on ECU (on-board) is essential to improve the transient performance of diesel engines. In the previous studies, the authors developed an on-board polytropic index prediction model for compression stroke that was solely applicable under steady conditions. In the present study, newly developed models were added to improve prediction of the polytropic index for compression stroke under transient driving conditions. The average and maximum errors of polytropic index under transient conditions compared to the result of 1-D engine simulation were 0.37% and 1.06%, respectively. Additionally, the calculation time of the model per cycle was 50.6 μs, sufficient for on-board calculation.

<p> The present study conducted the derivation of the empirical equation in terms of the heat transfer phenomena at the intake manifold of internal combustion engines and the implementation of its equation to 1-D engine simulation. The derived equation allows to calculate the Nusselt number at the intake system, which causes to predict the mass flow rate of intake air into the cylinder accurately, ultimately improving the fuel consumption by controlling the auto-ignition timing. The empirical equation was developed based on the Colburn equation, taking into consideration of the effects of the thermal boundary layer development and the intermittent air flow induced by the opening and closing of intake valves. Compared with the experimental data, the average errors of the Colburn equation and the empirical equation were estimated to be 91.1% and 2.7%, which gives to improve the prediction accuracy of the Nusselt number by deriving the empirical equation. The equation was then implemented in 1-D engine simulation and compared to the results of the Colburn equation, revealing the maximum and average intake air temperature differences of 11.4 K and 2.7 K, respectively.</p>

<p>For improvement of thermal efficiency of diesel engines, it is effective to control the fuel injection by using the model-based control (MBC) on the ECU (on-board) with cycle-by-cycle calculation. The authors previously developed an on-board in-cylinder wall temperature prediction model and wall heat transfer prediction model for MBC. For the validation of the developed models, the present study measured the time evolution of local wall temperature and pressure in the combustion chamber and calculated wall surface heat flux and evaluated the errors of heat loss results obtained from model. Also, the polytropic index prediction model was evaluated using the result of in-cylinder pressure. As a result, it was confirmed that heat loss results during compression and expansion strokes show 1.3% errors and polytropic index prediction model shows 0.1% errors comparing with experiment data.</p>

<p>Internal combustion engines have been required to improve the thermal efficiency and reduce the pollutant emission, and the previous studies were developed by controlling the air-to-fuel ratio and reducing the pressure fluctuations. For further improvement of the thermal efficiency, it is expected to model the heat transfer phenomena at the intake system and predict the air mass flow rate into the cylinder, which causes to keep the stoichiometric air-to-fuel ratio and improve the fuel consumption. The present study experimentally developed the empirical equation of the heat transfer at the intake system. This was based on Colburn's equation considering the development of the thermal boundary layer and the unsteady heat transfer phenomena, which was expressed by using the Reynolds, Graetz and Strouhal numbers. Compared with the experimental data and the present empirical equation, the maximum and average errors were estimated within 10.5% and 3.1%, respectively.</p>

Gasoline engines have been required to improve the thermal efficiency and reduce the pollutant emission, and the previous studies were developed by controlling the ignition timing and keeping the constant air-fuel ratio. For further improvement of the thermal efficiency, it is expected to reduce the pressure fluctuations due to the combustion per cycle, which causes to generate the stable combustion field and improve the fuel consumption. Since the pressure fluctuations due to the combustion are significantly affected by the ratio of the residual gas in the cylinder, the present study proposed the method to estimate the ratio of the residual gas, which is defined as the mass ratio of the residual gas and the air-fuel mixture into the cylinder, by using the combustion pressure, and developed the methods to reduce the pressure fluctuations considering the ratio of the residual gas by controlling the ignition timing. Under the experimental condition of the large ratio of the residual gas, it was found that the fluctuations of the indicated mean effective pressure was reduced to more than 20% by using the developed methods.

<p>This study presents an experimental optimization of the thermal efficiency of a short-stroke small engine with a supercharger, which has the advantage of high engine power and the shortcoming of increased loss of cooling from the combustion chamber walls. This shortcoming is responsible for the reduction of the net thermal efficiency. For improving the thermal efficiency, the present study considered using the lean mixture combustion, and optimized the valve lift, the valve overlap angle, the air-fuel ratio (A/F), the ignition timing, the boost pressure, and the surface treatment. Firstly, the valve lift and the valve overlap angle were changed, which lead to the reduction of the blowby and the blow-back gas. We investigated the effects of the A/F and the ignition timing on the engine torque and the brake specific fuel consumption rate (BSFC), and these results showed that it was possible to improve the BSFC, although the engine torque decreased along the overall engine speed range. Secondly, for the improvement of both the engine torque and the BSFC, we optimized the relationship between the boost pressure and the A/F and adapted the surface treatment, which lead to the reduction of the pumping and the friction losses. From the above optimizations, the averaged engine torque, the averaged BSFC and the maximum net thermal efficiency were improved by 6.3%, 10.9% and 38.8%, respectively.</p>

Measuring precise in-cylinder pressure traces of internal combustion engines is an important factor for estimating their performances. It is known that the actual pressure readings measured with piezoelectric pressure transducers have various forms of error. This paper is devoted to a study of compensation methods for reducing the errors caused by thermal shock. Numerical analysis was carried out for the error to derive the equations of error compensation using the actual pressure data. The results indicate that the error is corrected quite well with the obtained equations.

Measurement and analysis of burner flame spectrum with the biomass blended liquid fuel was done to investigate the combustion characteristics of biomass fuels. The experimental apparatus was mainly constructed of fuel vaporizing and mixing device, laminar flow burner, reflection spectroscope, and a digital camera. Four kinds of pure fuel and four kinds of blended fuel were used and the equivalence ratio was changed as the experimental parameter. As the results, it was obtained that the main radical luminescence existing in the flame, its changing tendency against the equivalence ratio, and the possibility of estimating the equivalence ratio with the ratio of luminous intensity of two different radical.

Temperature distribution in the near wall region was measured by real time holographic interferometry and high-speed video camera. As a result, temperature distribution, within the region from the wall surface to 0.1mm distance, could not be measured, because of the lack of the resolving power of designed optical system. However, the temperature distribution of the other region was measured by counting the number of interference fringes. In addition, the great change of temperature distribution as the flame approached toward the wall was measured.

Since, we derived that the luminous intensity of C_2 radical and CH radical can be described as an exponential function of the combustion pressure from the previous research, it becomes possible that supplied equivalent ratio is estimated from the luminous intensity ratio of radical. But, before applying this research to the engine that runs under the high temperature, it is necessary to examine the effect of the temperature change of mixture. Therefore, we did an experiment by using the optical unit and the constant volume combustion chamber, which made temperature change of mixture in the combustion chamber. Through analyzing the experimental result, we had concluded that the radical luminescence ratio is not affected by the change of the temperature of the mixture.

The distribution of luminous intensity of radicals, CH and C_2 were measured under atmospheric pressure and high combustion pressure. From the experiment with the premixed laminar burner, it could be confirmed that the radical luminescence distribution and the distribution of radical luminous intensity ratio could be measured. And it was found that the luminous intensity of CH radical was greater than that of C_2 radical and the value of luminous intensity ratio became small as the mixture became rich. From the experiment with the combustion chamber, it was also found that the luminous intensity became strong as the combustion pressure rose and the value of luminous intensity ratio became large as the combustion pressure rose.

The purpose of this study is to establish a method to improve the accuracy of acquiring pressure trace of an internal combustion engine. Inaccuracy in acquiring pressure trace is caused by the thermal deformation of the diaphragm of a pressure transducer and the electric circuit characteristic of a charge amplifier. A correcting equation for inaccuracy caused by the thermal deformation was acquired by analyzing the deformation model of the diaphragm of the pressure transducer used in the experiment with a burner. As for the imaccuracy caused by the electric circuit characteristic of the charge amplifier, correcting equation was acquired by analyzing the simplified electric circuit of charge amplifier. By applying these equations, a method of improving the accuracy of pressure trace for four types of water-cooled pressure transducer was established.

The thire paper examined the effect of turbulence by combustion causes to heat loss. But in real gasoline engine, the air fuel mixture, which inhaled it in cylinder includes initial turbulence. Therefore effect of initial turbulence of mixture was examined to estimate heat loss of gasoline engine in this paper. The initial turbulence was expressed using a simple model in which the momentum of turbulence damps when turbulence moves from unburned gas to burned gas. The expression to estimate heat loss is expressed as next by using the model. [numerical formula] Where the third term expressed the effect of initial turbulence and the coefficient: Cd&ap;0.24 has expressed damping of initial turbulence.