High-pressure droplet combustion studies

This is a joint research program, pursued by investigators at the University of Tokyo, UCSD, and NASA Lewis Research Center. The focus is on high-pressure combustion of miscible binary fuel droplets. It involves construction of an experimental apparatus in Tokyo, mating of the apparatus to a NASA-Lewis 2.2-second drop-tower frame in San Diego, and performing experiments in the 2.2-second tower in Cleveland, with experimental results analyzed jointly by the Tokyo, UCSD, and NASA investigators. The project was initiated in December, 1990 and has now involved three periods of drop-tower testing by Mikami at Lewis. The research accomplished thus far concerns the combustion of individual fiber-supported droplets of mixtures of n-heptane and n-hexadecane, initially about 1 mm diameter, under free-fall microgravity conditions. Ambient pressures ranged up to 3.0 MPa, extending above the critical pressures of both pure fuels, in room-temperature nitrogen-oxygen atmospheres having oxygen mole fractions X of 0.12 and 0.13. The general objective is to study near-critical and super-critical combustion of these droplets and to see whether three-stage burning, observed at normal gravity, persists at high pressures in microgravity. Results of these investigations will be summarized here; a more complete account soon will be published

Variations in Δ14C of POC in Waters from the Upper to Lower Ishikari River

[研究報告

Optimization Of Flame Stabilization Limits In Meso-Scale Tube Combustors With Wire Mesh

In the last two decades, with the continued depletion of energy resources and the need for better power sources for small scale devices, researchers have become increasingly interested in meso and micro-scale combustion. Flame stability of a meso-scale combustor depends on a few important factors such as combustor wall thickness, wall thermal conductivity and inner diameter. In order to enhance the combustor performance such as the operational limits, it is vital to fundamentally understand these determinant factors. In this research, simulations and experiments were performed to investigate the factors affecting the flame stabilization in meso- scale tube combustors with stainless steel wire mesh. The inner diameter of the meso-scale cylindrical tube combustors is fixed to 3.5 mm while the wall thickness is maintained at 0.7 mm. The wire mesh is located between the unburned and burned gas region of the combustor. The numerical simulations were performed using a three-dimensional (3-D) numerical model, from which the results in terms of gas and wire mesh temperature contours, blowout limits, combustor outer wall temperature distribution and combustion efficiency were established. In the experiments, the equivalence ratio and mixture flow velocity were varied and the effects in terms of flame stabilization limits were recorded. The main objective of utilizing a 3-D numerical model is to successfully demonstrate the role of thermal path from the tube combustor wall to the wire mesh in enhancing the flame stabilization near the blowout limits. The numerical results show that the direction of the thermal path plays a significant role in improving the blowout limits. It is also demonstrated that more heat can be recirculated to the unburned gas region with the use material with higher wall thermal conductivity in burned gas region. As a result, the flame stabilization limits can be enhanced

Prolonged maturation of prefrontal white matter in chimpanzees

Delayed maturation in the prefrontal cortex, a brain region associated with complex cognitive processing, has been proposed to be specific to humans. However, we found, using a longitudinal design, that prefrontal white matter volume in chimpanzees increased gradually with age, and the increase appears to continue beyond the onset of puberty, as in humans. This provides the first evidence for a prolonged period of prefrontal connection elaboration in great apes

High-pressure combustion of binary fuel sprays

The ultimate objective of this study is to obtain fundamental information relevant to combustion processes that occur in fuel sprays of practical interest at high pressures in internal combustion engines. Since practical fuels are multicomponent and derived from petroleum, the present work involves the model alkane mixture of n-heptane and n-hexadecane. Since burning droplets in sprays can interact with each other, the present work involves investigation of the effects of this interaction on flame shapes and droplet burning times. The small droplets in practical combustion chambers are not significantly influenced by buoyancy. Since such small droplets are difficult to study experimentally, the present work takes advantage of microgravity to lessen buoyancy and enable information about droplet interactions to be obtained by studying larger droplets. The results are intended to provide fundamental understanding that can be used in improving descriptions of practical spray combustion

Flame-Spread Behavior Of Biodiesel (B20) In A Microgravity Environment

Indonesia has implemented a policy of using diesel fuel containing 20 percent biofuel (commonly known as B20 biodiesel), as stated in Energy and Mineral Resources Ministerial Decree No. 23/2013. This study investigated the flame-spread characteristics of biodiesel (B20) in a microgravity environment through drop tower facilities. This is due to the difficulty in creating droplet sizes similar to the real liquid sprays in the combustion chamber of diesel engines. The experiment used biodiesel (B20) droplets with a diameter 1 mm. The results show that the biodiesel (B20) droplets have characteristics of a flame–spread limit distance SBC/dC0limit = 7. This paper discusses the characteristics of biodiesel (B20) droplets in detail

Flame Stabilization In Multiple Inlet Channel Meso-Scale Tube Combustors With Wire Mesh

Micro combustion system is one of potential solutions that provides better energy requirement for small-scale devices as compared to conventional batteries. Very recently, quite a number of works have been performed to enhance the combustion stability of meso and micro-scale combustors. Researchers and engineers are diligently experimenting various design of micro combustors with the ultimate objective of having reliable burner. In this study, a meso-scale tube combustor with multiple inlet channel is proposed. Stainless steel wire mesh is utilized as the flame holder, which is located between the unburned and burned gas region. The combustion take place in a channel with 3.5 mm diameter. Aluminium is selected as the material of the combustor considering the limitation of fabrication technology. A three dimensional (3-D) model is utilized to demonstrate the combustion of propane-air mixture in the designed combustor. The results in terms of streamline velocity pattern, heat of reaction, wire mesh and outer wall temperature are established. It is shown in this paper that flame can be stabilized in the tube combustor. Nevertheless, the proposed combustor is only at a preliminary design where there are quite a number of important parameters that need to be obtained before going into fabrication stage. One of the important examples is flame blow out limits

Compartment Syndrome after Prostatectomy

Robot-assisted laparoscopic prostatectomy (RALP) for prostate cancer was introduced in 2000 and rapidly gained popularity. The Da Vinci Surgical System® can ensure improved local control of cancer and fewer perioperative complications. However, RALP is performed in the steep-Trendelenburg position (a combination of lithotomy and head-down tilt position / Lloyd-Davies position) to obtain a good surgical view, and as a result, well leg compartment syndrome (WLCS) can become a serious complication of RALP. Here, we report a case of WLCS after RALP. A 75-year-old man underwent surgery for prostate cancer and immediately complained of pain and numbness after surgery. The pressure of the four leg compartments increased. Ultimately, we diagnosed the patient with WLCS in his right leg, and an emergency fasciotomy was performed. He completely recovered with no permanent disability and was discharged one month after rehabilitation. Although WLCS after RALP is a rare and severe complication, the patient recovered completely with early diagnosis and intervention. Measuring the compartment pressure is useful when the patient is drowsy immediately after recovery from anesthesia. Preventing WLCS requires identifying this condition as a potential complication of RALP and all urologic surgeries performed in the lithotomy position

Primary leiomyoma of the bladder

The case presented is of a 47-year-old patient with an extravesical pedunculated bladder leiomyoma, which was difficult to distinguish from a retroperitoneal tumor. Preoperatively, it was suspected to be a retroperitoneal tumor and a laparotomy with tumor resection was performed. lntraoperatively, the bladder and tumor were connected by a cord-like tissue. A retrospective review of preoperative images revealed that cord-like tissue, identified intraoperatively, was also present. Bladder leiomyomas can grow as extravesical pedunculated tumors. Therefore, when the continuity between the bladder and tumor is only a cord-like object, the finding of continuity is useful to diagnose with bladder leiomyoma

Quantifying Heat Losses In Micro Combustor With Wire Mesh Using Numerical Simulation

Micro power generation system is a field of study that has come into interest by many researchers due to the strong demands for low weight and long-life power sources of electronic devices. These has led to the increasement of meso and micro-scale combustion investigations. In order to fully understand more on this field of study, a numerical stimulation is utilized to investigate the effect of heat recirculation on the blowout limit for micro combustion. Four different combination of tube combustors is used to investigate their blowout limit such as quartz-brass tube combustion combination for unburned-burned region of micro combustor tube. The combination of tube combustors is then investigated using three-dimensional (3D) numerical simulation. The results suggested that by utilizing brass tube on either region of unburned or burned tube is able to improve the value of heat conducted on inner wall of via inner wall of the tube greatly. Due to the conductivity of brass tube is much larger than quartz tube, the improvement is expecte