Amount Of Airflow Research Articles

Influence of inlet boundary conditions on 3D steady RANS simulations of non-isothermal mechanical ventilation in a generic closure

Inlet boundary conditions at the supply opening play an important role in the accuracy and reliability of computational fluid dynamics (CFD) simulations for indoor airflow. A non-exhaustive overview of past CFD simulations of ventilation flow in generic enclosures indicates that uniform hypotheses of inlet boundary conditions are commonly used. However, due to thermal effects and a complex air supply system geometry, constant values of inlet airflow quantities can be insufficient for an accurate simulation of non-isothermal ventilation flow. In addition, this can lead to biased conclusions on the performance of turbulence models and other computational settings. To assess this issue, a well-documented experiment on non-isothermal mechanical ventilation with detailed information of inlet conditions from the literature is used in this study. Different turbulence models and inlet boundary conditions are validated, including seven steady Reynolds-averaged Navier-Stokes (RANS) models, six methods of imposing inlet air velocity, three methods of specifying air temperature, and a wide range of turbulence quantities. The parametric study demonstrates that in this particular case, i.e., cold air supply from a single round nozzle diffuser close to the ceiling, ω-based turbulence models perform better than the ε-based turbulence models. The impacts of different methods to specify inlet air temperature profile and turbulence quantities on the simulation results are not significant. However, if the inlet airflow direction is not taken into account appropriately, significant deviations are observed between CFD simulations and experimental data.

Compact Incremental Random Weight Network for Estimating the Underground Airflow Quantity

Optimal operation of an actual mine main fan switchover process relies heavily on a good measurement of underground airflow quantity (UAQ). However, real-time measuring the UAQ is difficult using conventional measurement techniques. In this article, a novel randomized learning model, named compact incremental random weight network (CIRWN), is proposed to estimate the UAQ. Since the hidden parameters of the original IRWN are generated in a fixed scope with a random manner, which is prone to create redundant hidden nodes, a CIRWN with new inequality constraints is proposed. The inequality constraints have several attractive properties, including dynamically guiding the generation of hidden parameters, effectively enhancing the convergence rate, and successfully establishing a universal approximator. Experiments using four benchmark datasets and an industrial dataset show that the established model possesses a more compact network structure and better modeling accuracy as well as faster convergence rate compared with other methods.

Improvement of Working Conditions and Opinions of Mine Workers When Battery Electric Vehicles (BEVs) Are Used Instead of Diesel Machines \u2014 Results of Field Trial at the Kittil\xe4 Mine, Finland

A major part of the European Union’s (EU) project Sustainable Intelligent Mining System (SIMS) is investigating the development of diesel-free/carbon–neutral underground mines in order to ensure sustainable underground mining in the future. Replacing diesel machines with electric vehicles in underground hard rock mines has been widely acknowledged by the mining industry worldwide as a critical step to improve working conditions by reducing diesel exhaust–related contaminants, to reduce mine ventilation electrical power cost by reducing mine airflow quantity, and to reduce mine greenhouse gas emissions. All of these are major requirements to achieve sustainable future underground mining practices. A field trial of Epiroc’s 2nd generation of Battery Electric Vehicles (BEVs) at Agnico Eagle Finland’s Kittilä mine was conducted during 2019–2020. Vehicles tested were MT42 mine truck, ST14 Load-Haul-Dump (LHD), and Boomer E2 jumbo drill rig. This paper outlines the improvement of the working conditions observed in the field trial, and the opinions of the mine personnel at Kittilä mine on using BEVs instead of diesel machines. Measurements of atmospheric contaminants and air temperatures taken during the field trial clearly demonstrated a significant improvement of working conditions when BEVs were operating as opposed to diesel machines. This field observation was supported by the opinion of the majority of the Kittilä mine workers. However, some remaining concerns must be addressed before BEVs can replace diesel machines.

Evaluating the effect of midpalatal corticotomy-assisted rapid maxillary expansion on the upper airway in young adults using computational fluid dynamics.

Midpalatal corticotomy-assisted rapid maxillary expansion (MCRME) is a minimally invasive treatment of maxillary transverse deficiency (MTD) in young adults. However, the effect of MCRME on respiratory function still needs to be determined. In this study, we evaluated the changes in maxillary morphology and the upper airway following MCRME using computational fluid dynamics (CFD). Twenty patients with MTD (8 males, 12 females; mean age 20.55 years) had cone-beam computed tomography (CBCT) images taken before and after MCRME. The CBCT data were used to construct a three-dimensional (3D) upper airway model. The upper airway flow characteristics were simulated using CFD, and measurements were made based on the CBCT images and CFD. The results showed that the widths of the palatal bone and nasal cavity, and the intermolar width were increased significantly after MCRME. The volume of the nasal cavity and nasopharynx increased significantly, while there were no obvious changes in the volumes of the oropharynx and hypopharynx. CFD simulation of the upper airway showed that the pressure drop and maximum velocity of the upper airway decreased significantly after treatment. Our results suggest that in these young adults with MTD, increasing the maxillary width, upper airway volume, and quantity of airflow by MCRME substantially improved upper airway ventilation.

The optimization of a dust suppression and clean production scheme in a TBM-constructed tunnel based on an orthogonal experiment

This study aims to examine whether clean production can be achieved by using a ventilation dust removal system in a tunnel being constructed using a tunnel boring machine (TBM). The section between the Guizhou-Road Station and the Guipaijing Station on the No. 1 line of the Qingdao Metro was selected as the study area, and the effectiveness of a ventilation dust removal system on the diffusion distance and mean concentration of dust in the excavating area was investigated through the use of a CFD-based numerical simulation. Firstly, it was found that when the first pressure quantity, exhaust quantity, and position of the pressure inlet and exhaust inlet of the ventilation dust removal system all remained unchanged, the secondary pressure quantity corresponding to the optimal dust suppression effect was determined to be 8 m³/s. Next, an orthogonal experiment was performed on the position of the pressure inlet and exhaust inlet and the forced-to-absorbed airflow quantity ratio in order to examine the effect of different combinations on the dust suppression effect in the tunnel. By selecting the dust diffusion distance, mean dust concentration in the tunnel and dust-collecting efficiency as the evaluation indexes, three favorable schemes were determined, from which the optimal scheme was selected. In the optimal combination, the secondary pressure inlet and exhaust inlet were 28 m and 11m away from the tunnel face respectively and the forced-to-absorbed airflow quantity ratio was 1.6. After the scheme’s optimization, the dust diffusion distance in the tunnel was shortened considerably by 53 %, the mean dust concentration was reduced to 1.52E-06 kg/m³, and the dust-collecting efficiency was enhanced by 13.19 %. Under these optimal conditions, a ventilation dust removal system can maximize the operational efficiency and ensure a clean air environment during any production activities.

Study of airflow induced by regular particles in freefall through tubes

Airflow induced by falling particles can be a significant factor in causing dust emission during the conveyance of bulk materials. Heretofore, there have been few experimental studies on the effect of the particle size and the diameter of the tubes through which they are falling on the induced airflow. This study involved the experimental analysis of the correlation between those two factors and the induced airflow. The results were as follows: within the range of the total drag coefficient (0.62–0.94) of the experimental setup, the induced airflow velocity increased with an increment of the mass flow rate of the particles and drop height, and the power exponents of a fitted curve were approximately 0.35 and 1.29, respectively. Within the particle diameter range of 3.247–9.223 mm, the power coefficients and power exponents of a fitted curve for induced airflow velocity increased from 0.224 and 0.269 to 0.458 and 0.384, respectively, with the increase in particle size. As the tube diameter decreased from 200 mm to 120 mm, both the induced airflow velocity and the quantity of specific induced airflow increased, while the quantities decreased when the tube diameter decreased from 120 mm to 75 mm. The semi-empirical equation of the induced airflow velocity was established to predict the quantity of induced airflow under various operation conditions.

Rapid maxillary expansion effects of nasal airway in children with cleft lip and palate using computational fluid dynamics.

Rapid maxillary expansion (RME) improves nasal airway ventilation in non-cleft palate children. Children with unilateral cleft lip and palate (UCLP) may have nasal obstruction and experience an increased risk of obstructive sleep apnoea. The effect of RME in UCLP children is unclear. This retrospective study evaluated RME-induced changes in ventilation parameters in children with UCLP using computational fluid dynamics. Nineteen patients (10 boys, mean age 10.7years) who required RME had cone-beam computed tomography images taken before and after RME. Twenty control participants (11 boys, mean age 11.1years) received regular orthodontic treatment. Nasal airway ventilation parameters (air pressure, air velocity and airflow rate) were analysed via computational fluid dynamics, and nasal cross-sectional area (CSA) was measured. Maximum pressure, velocity and nasal resistance were significantly reduced by RME in the UCLP group. Air flow rate and CSA on the cleft side significantly were increased by RME in the UCLP group. In children with UCLP, increasing the quantity of airflow and CSA on the cleft side by RME substantially improved nasal ventilation.

Modeling and control of mine main fan switchover system

Mine main fan switchover system (MMFSS) is crucial for the mine safe production. MMFSS consists of two main fans (one working and one on standby), and each main fan is equipped with a vertical air door and a horizontal air door. The main purpose of MMFSS is to ensure the stability of the underground airflow quantity and achieve the satisfactory ventilation during the switchover. Moreover, the safe and economic operation of mine production should be ensured. In this paper, the modeling and control problem of MMFSS is considered. First, based on the theory of fluid flow network, the minimal model of MMFSS is built by combining the branch fluid dynamics with the concept of graph theory. Then, a decentralized controller that fully considers the pressure head regulation of two main fans is developed by the Lyapunov stability theory. The controller can ensure that the four air doors can meet with the technological requirements. Finally, the proposed results are conformed using simulations on a semi-physical simulation platform for MMFSS.

Ventilation Requirements for Today's Mechanized Underground Metal Mines

Ventilation is a basic part of all underground mine operations. The main objective of underground mine ventilation is to provide sufficient quantities of air to all the working areas. Today, in modern mechanized underground metal mines, diesel-powered mobile equipment is extensively used for high production rates. Ore can be extracted from many production stopes due to the production rate in a mine. Amount of airflow required for an underground mine depends on several factors, including daily production capacity, number of diesel equipment, ambient temperature, mining method, mining depth and airway type. After implementation of Stage IV Emission Standards for nonroad diesel engines, it is getting more complex to determine airflow quantities required for underground mines wherefore reduced diesel emissions. Required amount of airflow for a mine is obtained by ventilation fans and the largest cost aspect in mine ventilation is the power costs of running the ventilation fans which can reach as high as 50 percent of a mine’s entire electrical power cost. The cost of electrical power has increased significantly in recent years and is likely to continue increasing in the future. That is why it is getting more important to determine proper ventilation design for underground metal mines.

Multiple models and neural networks based adaptive PID decoupling control of mine main fan switchover system

Mine main fan switchover system (MMFSS) consists of two main fans, which are equipped with a horizontal air door and a vertical air door, respectively. The purpose of operating MMFSS is to ensure small fluctuation of the underground airflow quantity and to guarantee safe operations of both fans simultaneously by controlling the four air doors during switchover from working to standby fan. MMFSS has time-varying dynamics under different operating conditions, strong coupling, high non-linearities and uncertainty in character, applying conventional control methods can not lead to satisfactory performances. In this study, an adaptive intelligent decoupling proportional–integral–derivative (PID) control method is proposed, where the unmodelled dynamics are estimated and compensated by neural networks, the coupling effect is eliminated by the designed decoupling compensator, and a switching mechanism among multiple models is employed to deal with the effect of time-varying dynamics. By inspiring from the generalised minimum variance control law concept, the parameters of the developed controller are determined. The stability of the close-loop system and the convergence of tracking error are examined. Finally, simulations of MMFSS show the feasibility and effectiveness of the obtained results.

The impacts of the axial-to-radial airflow quantity ratio and suction distance on air curtain dust control in a fully mechanized coal face.

To understand the impacts of the axial-to-radial airflow quantity ratio (denoted as R) and the suction distance (denoted as Ds) on air curtain dust control in a fully mechanized coal face, the 3down610 coal face in Jiangzhuang coal mine was numerically simulated in this study. A mathematic model was established to describe the airflow migration and dust diffusion in a coal face, and a scaled physical model was constructed. The comparison between simulation results and field measurements validated the model and the parameter settings. Furthermore, the airflow migration and dust diffusion at various R and Ds are analyzed using Ansys CFD. The results show that a reduction of R and Ds is conducive to the formation of an effective axial dust control air curtain; the dust diffusion distance decreases with the decrease of both R and Ds. By analyzing the simulation results, the optimal parameter for air curtain dust control in the 3down610 coal face and those faces with similar production conditions is determined as R = 1/9 and Ds = 2m. Under the optimal parameter condition, the high-concentration dust can be confined in front of the mining driver within a space 5.8m away from the coal face.

Modelling electro-thermal response of lithium-ion batteries from normal to abuse conditions

Insight of thermal behaviour of lithium-ion batteries under various operating conditions is crucial for the development of battery management system (BMS). Although battery thermal behaviour has been studied by published models, the reported modelling normally addresses either normal operation or thermal runaway condition. A comprehensive electro-thermal model which can capture heat generation, voltage and current variation during the whole process from normal cycling to thermal runaway should be of benefit for BMS by evaluating critical factors influencing potential transition to thermal runaway and investigating the evolution process under different cooling and environment conditions. In this study, such a three-dimensional model has been developed within the frame of open source computational fluid dynamics (CFD) code OpenFOAM to study the electrical and thermal behaviour of lithium-ion batteries (LIBs). The equations governing the electric conduction are coupled with heat transfer and energy balance within the cell. Published and new laboratory data for LiNi0.33Co0.33Mn0.33O2/Li1.33Ti1.67O4 (LNCMO/LTO) cells from normal cycling to thermal runaway have been used to provide input parameters as well as model validation. The model has well captured the evolution process of a cell from normal cycling to abnormal behaviour until thermal runaway and achieved reasonably good agreement with the measurements. The validated model has then been used to conduct parametric studies of this particular type of LIB by evaluating the effects of discharging current rates, airflow quantities, ambient temperatures and thickness of airflow channel on the response of the cell. Faster function losses, earlier thermal runaway and higher extreme temperatures were found when cells were discharged under higher current rates. The airflow with specific velocity was found to provide effective mitigation against over-heating when the ambient temperature was below 370K but less effective when the ambient temperature was higher than the critical value of 425K. The thickness of airflow channel was also found to have critical influence on the cell tolerance to elevated temperatures. These parametric studies demonstrate that the model can be used to predict potential LIB transition to thermal runaway under various conditions and aid BMS.

Effects of radial air flow quantity and location of an air curtain generator on dust pollution control at fully mechanized working face

To better understand the effects of radial air flow quantity and the location of air curtain generator on dust pollution control, the 2–1092 fully mechanized working face in Xinzhi coal mine (Huozhou Coal Electricity Group Co., Ltd., Shanxi, China) was numerically simulated in the present study. A full-scale physical model of the working face was established; then, based on airflow-dust particle two-phase flowing characteristics, the k-ε-Θ-kp mathematical model was constructed. The comparison between simulation results and field measurements validated the model and the parameter settings. Furthermore, the effects of ventilation parameters on airflow migration and dust diffusion were numerically investigated using FLUENT. The results show that the increase of the radial air flow quantity (denoted as φ) and the distance of the air curtain generator from working face (denoted as dw) is beneficial to the formation of a dust-control air curtain. At a constant dw, the dust diffusion distance (denoted as D) decreases with the increase of φ. At a constant φ, D decreases with the increase of dw when a dust-control air curtain is formed; otherwise, the increase of dw leads to the increase of D. By analyzing the simulation results, the optimal ventilation parameters for 2–1092 fully mechanized working face and those working faces under similar production conditions are determined as: φ=240–270m3/min and dw=20–30m.

Coupling of EIT with computational lung modeling for predicting patient-specific ventilatory responses.

Providing optimal personalized mechanical ventilation for patients with acute or chronic respiratory failure is still a challenge within a clinical setting for each case anew. In this article, we integrate electrical impedance tomography (EIT) monitoring into a powerful patient-specific computational lung model to create an approach for personalizing protective ventilatory treatment. The underlying computational lung model is based on a single computed tomography scan and able to predict global airflow quantities, as well as local tissue aeration and strains for any ventilation maneuver. For validation, a novel "virtual EIT" module is added to our computational lung model, allowing to simulate EIT images based on the patient's thorax geometry and the results of our numerically predicted tissue aeration. Clinically measured EIT images are not used to calibrate the computational model. Thus they provide an independent method to validate the computational predictions at high temporal resolution. The performance of this coupling approach has been tested in an example patient with acute respiratory distress syndrome. The method shows good agreement between computationally predicted and clinically measured airflow data and EIT images. These results imply that the proposed framework can be used for numerical prediction of patient-specific responses to certain therapeutic measures before applying them to an actual patient. In the long run, definition of patient-specific optimal ventilation protocols might be assisted by computational modeling.NEW & NOTEWORTHY In this work, we present a patient-specific computational lung model that is able to predict global and local ventilatory quantities for a given patient and any selected ventilation protocol. For the first time, such a predictive lung model is equipped with a virtual electrical impedance tomography module allowing real-time validation of the computed results with the patient measurements. First promising results obtained in an acute respiratory distress syndrome patient show the potential of this approach for personalized computationally guided optimization of mechanical ventilation in future.

Validation of Contamination Control in Rapid Transfer Port Chambers for Pharmaceutical Manufacturing Processes.

There is worldwide concern with regard to the adverse effects of drug usage. However, contaminants can gain entry into a drug manufacturing process stream from several sources such as personnel, poor facility design, incoming ventilation air, machinery and other equipment for production, etc. In this validation study, we aimed to determine the impact and evaluate the contamination control in the preparation areas of the rapid transfer port (RTP) chamber during the pharmaceutical manufacturing processes. The RTP chamber is normally tested for airflow velocity, particle counts, pressure decay of leakage, and sterility. The air flow balance of the RTP chamber is affected by the airflow quantity and the height above the platform. It is relatively easy to evaluate the RTP chamber′s leakage by the pressure decay, where the system is charged with the air, closed, and the decay of pressure is measured by the time period. We conducted the determination of a vaporized H2O2 of a sufficient concentration to complete decontamination. The performance of the RTP chamber will improve safety and can be completely tested at an ISO Class 5 environment.

Numerical simulation of ventilation and dust suppression system for open-type TBM tunneling work area

In order to study the characteristics of the ventilation and dust suppression system for open-type TBM tunneling work area in a Ø8.53 diversion project, the numerical simulation method is adopted, and a three-dimensional steady airflow model, a dust flow model as well as other related flow characteristic equation models are established by considering the dust production mechanism of TBM construction. Besides, corresponding simulation models validated by experiment are established using CFD software, and the impacts of the main vent location, the air baffle length in the main beam and the exhausting air flow quantity on flow field distribution and dust flow behavior in open-type TBM tunneling work area are investigated. The results show: when the main vent is located 70–80m away from the working face, the ventilation in TBM tunneling work area is optimal; when the air baffle is as long as the main beam, the dust collection efficiency is the highest, reaching 89.4%; under the condition that the exhausting air flow quantity is less than half of the ventilation air flow quantity required by energy consumption and the minimum backflow velocity, the best dust suppression effect can be achieved when the exhausting air flow quantity is 40% of the ventilation air flow quantity.

CFD modelling of ventilation optimization for improving mine safety in longwall working faces

Mining coal seams with high coal gas content and coal spontaneous combustion (SponCom) risk is often a challenge for mining engineers. Control measures for maintaining the gas concentration under the regulation permissible limit (Generally 1%) as well as reducing coal fire risks must be taken simultaneously in order to create safety production conditions. However, in reality, such measures either for gas or for fire problems are sometimes conflictive. For an example, the basic strategy of gas control in underground is to increase the ventilation airflow for sweeping the longwall working face and diluting the gas concentration, but it also results in leakage of an amount of air into the mine gob area sufficient to support the coal SponCom development process. Conversely, sealing or isolating mine gob areas can easily cause the gas accumulation which may increase the gas explosion risk. To conquer this dilemma situation, it is necessary to deeply understand the coupling relationship between the mine gases and coal SponCom controls. In this paper, based on a real case in an underground coal mine, a ventilation parameters optimization research is conducted by using the Computational Fluid Dynamics (CFD) simulation approach for solving the stated contradiction problems to derive the optimum solutions for both managing gas hazards and fire risks in the underground. In this study, the boundary conditions are fully considered in accordance with the reality. A list of important ventilation parameters including the air quantity supplied to the mine working face, the negative ventilation pressure in the roof roadway for gas drainage and reasonable distributed airflow quantity in tailgate roadways, are investigated. The research findings balance the requirements both for gas control and fire-prevention. The proposed method could be applied to guide the mine design practices in improving safety.

Examination of a newly developed mobile dry scrubber (DS) for coal mine dust control applications.

The Office of Mine Safety and Health Research of the U.S. National Institute for Occupational Safety and Health (NIOSH OMSHR) conducted laboratory testing of a self-tramming, remotely controlled mobile Dry Scrubber (DS) that J.H. Fletcher and Co. developed under a contract with NIOSH OMSHR to reduce the exposure of miners to airborne dust. The scrubber was found to average greater than 95 percent dust removal efficiency with disposable filters, and 88 and 90 percent, respectively, with optional washable filters in their prewash and post-wash test conditions. Although the washable filters can be reused, washing them generated personal and downstream respirable dust concentrations of 1.2 and 8.3 mg/m3, respectively, for a 10-min washing period. The scrubber's velocity-pressure-regulated variable-frequency-drive fan maintained relatively consistent airflow near the targeted 1.42 and 4.25 m3/s (3,000 and 9,000 ft3/min) airflow rates during most of the laboratory dust testing until reaching its maximum 60-Hz fan motor frequency or horsepower rating at 2,610 Pa (10.5 in. w.g.) of filter differential pressure and 3.97 m3/s (8,420 ft3/min) of scrubber airflow quantity. Laboratory sound level measurements of the scrubber showed that the outlet side of the scrubber was noisier, and the loaded filters increased sound levels compared with clean filters at the same airflow quantities. With loaded filters, the scrubber reached a 90 dB(A) sound level at 2.83 m3/s (6,000 ft3/min) of scrubber airflow, indicating that miners should not be overexposed in relation to MSHA's permissible exposure level - under Title 30 Code of Federal Regulations Part 62.101- of 90 dB(A) at or below this airflow quantity. The scrubber's washable filters were not used during field-testing because of their lower respirable dust removal efficiency and the airborne dust generated by filter washing. Field-testing the scrubber with disposable filters at two underground coal mine sections showed that it could clean a portion of the section return air and provide dust reduction of about 50 percent at the face area downstream of the continuous-miner operation.

Reaction characteristics and kinetics of gallium in chlorination roasting of copper tailings using calcium chloride

The mineral composition of copper tailings was examined, and the phase analysis of gallium was conducted for recovery of the rare scattered metal gallium from copper tailings. The reaction characteristics and kinetics of gallium in the chlorination roasting of copper tailings were investigated in a tube furnace apparatus under different conditions, including roasting temperature, quantity of chlorination agent, roasting time, and airflow. Calcium chloride was chosen for the chlorination reaction because it is highly effective for volatilization of metals. The results show that gallium mainly exists in limonites in the form of oxides, and increases in roasting temperature, quantity of chlorination agent, and roasting time are conducive to increasing the chloridizing volatilization rate of gallium. The tailings gradually melt when the roasting temperature exceeds 900 °C, resulting in a decrease in the chloridizing volatilization rate of gallium. The chloridizing volatilization rate of gallium reaches 78.86 % at roasting temperature of 900 °C for 40 min, airflow of 0.1 m3·h−1, and calcium content of 33.33 wt%. Study of the reaction kinetics of gallium in chlorination roasting shows that the values of activation energy both for chemically controlled and diffusion-controlled reactions are 44.64 and 11.93 kJ·mol−1, respectively. This indicates that the chemical reaction serves an important function in the chlorination volatilization of gallium. Taken together, the results reveal the usefulness of tailings as a source of rare metals and provide a basis for gallium recovery and environmentally friendly disposal of copper tailings.

An experimental study of the high-load extension of a homogeneous charge compression ignition engine with gasoline and n-heptane

With a combination of dual-fuel injection and exhaust gas recirculation or intake air temperature control to retard the homogeneous charge compression ignition combustion phase, the potential of expanding the homogeneous charge compression ignition load range was investigated. The experimental work was carried out on a real-time control dual-fuel homogeneous charge compression ignition operation test bench, which was based on a four-cylinder optimized kinetic process engine. It was observed that, with gasoline and n-heptane injection, the acceptable ranges of the exhaust gas recirculation rate and the intake air temperature were enlarged, and the load range of the homogeneous charge compression ignition engine was expanded. The intake air flow quantity can be raised by reducing the intake air temperature, and the indicated thermal efficiency of homogeneous charge compression ignition can be increased by utilizing sufficient n-heptane in the fuel. Compared with exhaust gas recirculation, intake air temperature control might be a better method to improve the indicated thermal efficiency of homogeneous charge compression ignition combustion. Also, from the viewpoint of deterioration in the emissions, exhaust gas recirculation is a better strategy for load expansion in homogeneous charge compression ignition with a high ratio of gasoline to fuel.