Incoming Air Research Articles

Evaluation of Variable Compressor Technologies

A diverse set of technology solutions are in development for reducing vehicular CO2 emissions. Beside the conventional internal combustion engine, there are hybrid powertrains, fuel cells and full electric vehicles. The challenge is finding the right technology that can be quickly implemented into production as a cost effective solution. In addition to CO2 reduction during vehicle operation, the impact of CO2 in the production and recycling of future vehicles must also be considered. From this perspective, the role of turbocharging is evolving, becoming more important for the future. It is an enabler for mature technologies known to improve engine efficiency like Miller timing, lean burn, increased exhaust gas recirculation (EGR) dilution and exhaust heat recovery. As a boosting device, improved turbocharging can also benefit other powertrain types like fuel cells. All previously mentioned applications benefit from wider compressor maps and higher compressor ratios. To achieve an extension of the performance map to areas of low mass flow rate, different methods have been discussed with the two most promising being trim reduction introduced by IAV’s Variable Trim Compressor (VTC) and swirl generation. The most common device for inducing a swirl onto the incoming airflow is to use swirl generating wings in front of the compressor wheel. However, Iwakiri explained that putting a single plate in front of the compressor wheel disturbs the recirculating flow, which acts positively to extend the compressor map. On this basis, plates were developed that guide the strongly swirled back flowing air in such a way that they impose a swirl on the incoming air. Trim reduction is well known for its ability to shift the surge line and maintain compressor efficiency. To achieve this, a conical element before the compressor wheel guides the incoming flow to the inner area of the wheel resulting in reduced flow separation. An orifice can also achieve almost the same effect but with much less axial extension. The advantages and disadvantages of these measures are explained using numerical (CFD) and experimental (turbocharger test bench) to show the potential of each approach. In summary trim reduction using a conical geometry is still the best performing approach. However, considering package restrictions, an orifice is also a good choice. Whereas swirl producing principles have a moderate impact on shifting the surge line. The extension of high mass flow rate is also of interest and this study shows a simple method to improve the compressor performance map in this area. A combination of the measures to expand the map in both directions is conceivable and is presented here as a concept.

High air flow-rate electrostatic sampler for the rapid monitoring of airborne coronavirus and influenza viruses

Capturing virus aerosols in a small volume of liquid is essential when monitoring airborne viruses. As such, aerosol-to-hydrosol enrichment is required to produce a detectable viral sample for real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) assays. To meet this requirement, the efficient and non-destructive collection of airborne virus particles is needed, while the incoming air flow rate should be sufficiently high to quickly collect a large number of virus particles. To achieve this, we introduced a high air flow-rate electrostatic sampler (HAFES) that collected virus aerosols (human coronavirus 229E, influenza A virus subtypes H1N1 and H3N2, and bacteriophage MS2) in a continuously flowing liquid. Viral collection efficiency was evaluated using aerosol particle counts, while viral recovery rates were assessed using real-time qRT-PCR and plaque assays. An air sampling period of 20 min was sufficient to produce a sample suitable for use in real-time qRT-PCR in a viral epidemic scenario.

CFD modelling of an animal occupied zone using an anisotropic porous medium model with velocity depended resistance parameters

The airflow in dairy barns is affected by many factors, such as the barn’s geometry, weather conditions, configurations of the openings, cows acting as heat sources, flow obstacles, etc. Computational fluids dynamics (CFD) has the advantages of providing detailed airflow information and allowing fully-controlled boundary conditions, and therefore is widely used in livestock building research. However, due to the limited computing power, numerous animals are difficult to be designed in detail. Consequently, there is the need to develop and use smart numerical models in order to reduce the computing power needed while at the same time keeping a comparable level of accuracy.In this work the porous medium modeling is considered to solve this problem using Ansys Fluent. A comparison between an animal occupied zone (AOZ) filled with randomly arranged 22 simplified cows’ geometry model (CM) and the porous medium model (PMM) of it, was made. Anisotropic behavior of the PMM was implemented in the porous modeling to account for turbulence influences. The velocity at the inlet of the domain has been varied from 0.1 m s−1 to 3 m s−1 and the temperature difference between the animals and the incoming air was set at 20 K. Leading to Richardson numbers Ri corresponding to the three types of heat transfer convection, i.e. natural, mixed and forced convection. It has been found that the difference between two models (the cow geometry model and the PMM) was around 2% for the pressure drop and less than 6% for the convective heat transfer. Further the usefulness of parametrized PMM with a velocity adaptive pressure drop and heat transfer coefficient is shown by velocity field validation of an on-farm measurement.

Effect of Oxygen Enrichment on Top Layer Sinter Properties

Properties like shatter index and yield of the top layer of iron ore sinter in a Dwight-Lloyd sintering machine have always been a bottleneck for improvement of overall sinter quality due to the practical limitation of achieving high sintering temperature and dwell time in the top layer. To improve the sinter yield and shatter index of top layer, various technologies like usage of additional coke breeze, gaseous fuel injection and oxygen enrichment have been reported. In this paper, effect of oxygen enrichment of the incoming air on top part of the sinter bed was investigated using pot sinter experiments with varying oxygen percentage of 0 to 12 vol.% in the incoming air for an initial duration of 1/3rd of the total sintering time. It was observed that with increasing oxygen percentage from 0 to 9 vol.% in the incoming air, top layer sinter yield increased from 76.1 to 80.6% and shatter index from 69.0 to 74.8%. The improvement in sintering properties were mainly attributed to the promotion of sintering reaction with improved time-temperature profiles specifically at the top layer which results in increase of phase fraction of Silico ferrites of calcium and aluminum (SFCA-I). However, beyond 9 vol.% oxygen enrichment, change in sinter properties was not significant. It is considered that excessive increase of oxygen enrichment does not contribute much to the increase of top layer peak temperature.

Spatial diversity of air temperature changes in Poland in 1961–2018

The article comprises an analysis of the spatial distribution, and variability of air temperature in Poland in the years 1961–2018. It was found that the mean increase in air temperature was 0.33 °C/10 years. The most evident warming occurred in the west of the country and at the Baltic Sea (> 0.4 °C/10 years). The greatest increase in the temperature was observed in summer (July 0.48 °C/10 years), winter (January 0.46 °C/10 years) and spring (April 0.41 °C/10 years), whereas in autumn the warming was not statistically significant. The major role of atmospheric circulation in shaping air temperature in Poland was corroborated. The positive correlation with the NAO was confirmed, and Pearson’s linear correlation coefficient (r) reached 0.81 in the north of Poland in January. An analysis of the variability of air temperature in Torun (Central Poland) in 1991–2018 demonstrated that the increase in temperature was correlated with a solar irradiance (r = 0.69 in July). Moreover, the types of atmospheric circulation and incoming air masses are also significant. The type of baric centre was found to play a very important role that is opposite in winter to what it is in summer. In cyclonic situations, air temperature increased in winter (r = 0.65 in January) and decreased in the warm half of the year (r = − 0.47 in September). An intensified flow of incoming air masses from the west caused air temperature to increase in winter (r = 0.72 in January) and to cool in summer (r = − 0.69 in August). The role of meridional flow becomes particularly evident in autumn (r = 0.49 in October).

Bi-objective dynamic weapon-target assignment problem with stability measure

In this paper, we develop a new bi-objective model for dynamic weapon-target assignment problem. We consider that the initial weapon assignment plan of defense is disrupted during engagement because of a destroyed air target, breakdown of a weapon system or a new incoming air target. The objective functions are defined as the maximization of probability of no-leaker and the maximization of stability in engagement order of weapon systems. Stability is defined as assigning same air target in sequence in engagement order of a weapon system so that reacquisition and re-tracking of air target are not required by sensors. We propose a new solution procedure to generate updated assignment plans by maximizing efficiency of defense while maximizing stability through swapping weapon engagement orders. The proposed solution procedure generates non-dominated solutions from which defense can quickly choose the most-favored course of action. We solve a set of representative problems with different sizes and present computational results to evaluate effectiveness of the proposed approach.

Numerical study of an integrated miniature ejector for catalytic micro-combustors

In the present study, an integrated micro-ejector was proposed to provide a mixture of n-butane and air for micro-combustors. The effects of fuel jet velocity and geometrical parameters of the ejector on the entrainment ratio were numerically investigated and theoretically analyzed. The results show that the incoming air mixes with the fuel jet flow through two routes. The entrainment ratio increases with an increasing fuel jet velocity due to the increased magnitude of negative pressure. Moreover, increasing the nozzle diameter leads to a sharp decrease in the entrainment ratio. However, the entrainment ratio can be drastically augmented by increasing the diameter of the mixing section. In addition, an increase in the length of mixing section will slightly decrease the entrainment ratio of the ejector. Furthermore, increasing the total area of air inlets gives rise to a drastic decrease in the entrainment ratio. These variation tendencies have a close relationship with the negative pressure contours. The findings of this study provide a guidance to the optimal design of this kind of micro-ejectors.

Heat pump system built into the room with the implementation of air exchange and microclimate

The efficiency and performance of an air heat pump system built into a room, together with supply and exhaust ventilation, currently requires a high-quality microclimate and clean air in the room. The transition in mass housing construction to the sealed windows with double-glazed windows, along with the positive factors such as a decrease in heat loss and a decrease in noise in rooms, led to a deterioration in the air regime in a room with traditional natural ventilation systems. In the winter period of space heating, energy is spent, among other things, on heating the incoming cold air, and in quite significant quantities. At the same time, the required level of air exchange is necessary in both poorly and well-insulated buildings. From this it follows that the heat consumption for ventilation without the use of special innovative engineering and technical solutions will not decrease from this, and the more insulated the building is, the higher in relative terms the ventilation costs will be. As a method for assessing the microclimate comfort, the authors propose the calculations and comparison of individual parameters of the thermal and humidity air regime for the room in accordance with the SanPiN standards. The supply and exhaust ventilation system with a heat exchanger (recuperation) has a number of advantages, which include: saving heat energy spent on heating the ventilation air, depending on the type of heat exchanger system; the efficiency level of air-thermal comfort in the room, due to the aerodynamic stability of the heat pump heating system and balanced heat exchange of the supply and exhaust air; the ability to maintain a minimum relative humidity in the supply and exhaust ventilation system in the range from 40 to 60%, in which viruses are the least viable. The recovered warm air is not just thrown out of the building, but enters a specially equipped mixing chamber with intensively uniform mixing, which allows achieving the efficiency factor of the heat pump COP = 3.5 and the ability to operate such an air heat pump system in climatic zones with the temperatures up to -25 °C.

Effect of wall cavity with combined fuel injection technique in scramjet combustor with CFD

The incoming air speed is too high which leads to less residence time inside the combustor. To address this problem the present article includes cavity at the combustor wall to create recirculation zone. The recirculation zone enhances the performance of the combustor. Two separate cases has been selected, one with the wall cavity and other is without cavity. The extreme changes are visualized in the flow field contours. As in the both cases, mixing efficiency approaches towards its maximum however the mixing length are seen to be different. It is observed that combustion efficiency is majorly influenced by the mixing of fuel with air. It is seen from this work that the generated shock waves play a dominant role for having efficient combustion. The hydrogen speed is varied in this work for 1 and 1.25 Mach numbers and it is observed that with shock strength, the combustion efficiency increases.

A stomata-inspired superhydrophobic portable filter system.

Stomata, specialized functional openings distributed on the leaf surface, are used for plant respiration by allowing gas exchange, i.e., taking in carbon dioxide and releasing oxygen, and for water content regulation. Their function is vital to plant survival. Leaves with different wettability exhibit different stomata densities. In this study, we find that stomata on Pistia stratiotes L. leaves are protected by superhydrophobic setae, which prevent direct contact between the stomata and water in humid environments by suspending water droplets on the top of the setae. Thus, oxygen and carbon dioxide are freely exchanged through the stomata. This structure inspired us to design and develop a mask for filtering solid particles and noxious gas from the atmosphere. The incoming gas is in convective contact with water, achieving a filtering efficiency. The solid particles and potential harmful gas in air are wetted and captured by water, leaving fresh air for healthy breathing. This novel design has potential applications in the treatment of respiratory diseases.

Performance investigations of cross flow indirect evaporative cooler

Dew point evaporative cooler is an indirect evaporative cooling (IEC) technique to lower temperature of incoming air below its wet bulb temperature and near to dew point temperature. The said technique does not involve any change in moisture content of incoming air. Performance parameters of dew point evaporative cooler are significantly influenced by configuration and structural arrangement of heat exchanger. The different arrangements of heat exchangers commonly used are counterflow, cross flow and counter-cross flow. This work presents performance investigations of cross flow indirect evaporative cooler. The cooling efficiencies and temperatures at the outlet of the cooler were investigated for different intake air temperatures and flow rates. Dew point evaporative cooling technique does not make use of compressor and harmful refrigerants hence would be a better option to conserve the environment and helps to reduce the emission of greenhouse gases.

Development and performance analysis of a PCM based cooling fan for hot climate of Bangladesh

In hot climatic regions, some kind of cooling system is necessary to avoid warmth and humidity. Many of the available cooling systems are not economic and sustainable. In this study, sustainable and feasible space/room cooling systems have been experimentally analyzed. A solar operated cooling system with two options have been designed and their performances are compared. Phase Change Material (PCM) is proposed to store thermal energy instead of a costly battery. A 1200-watt compressor and fin-type condenser are used to construct the vapor compression system. When the incoming air is passed through the cooling coil, it gets cool. For this cooling coil, 50 feet copper tube is used. The front side copper tube diameter of the fan is 3/8 inch and the backside tube diameter is 1/2 inch. It took about 35 minutes and 5 minutes to minimize the room temperature at the desired level in the case of the stand fan and duct fan, respectively. Furthermore, the stand fan and duct fan systems reduced 3 ℃ and 6 ℃ of the outside temperature, respectively.

Experimental Validation of a Portable Power and Cooling System Using Integrated TEG-ORC

A waste heat recovery system consisting of a hybrid power and cooling cycle is described in this paper. It couples a thermoelectric generator (TEG) and an organic Rankine cycle driving a vapor compression cycle to implement heat activated power and cooling. The system was designed, developed, and tested under laboratory conditions using a hot air source simulating a heavy-vehicle exhaust stream. The hybrid or so-called cofunctional power and cooling system was designed to approach the size of a fieldable unit for testing with mobile diesel generators or heavy-vehicle exhaust streams, which have strict requirements for size, weight, and efficiency. As a result, microchannel heat exchangers were used extensively throughout the system design. High-temperature bismuth telluride () thermoelectric (TE) modules were used, and the TEG section contained 20 modules in two distinct electrical strings sandwiched between microchannel cold-side and hot-side heat exchangers. The cofunctional system has shown stable operation during tests conducted at various incoming hot air temperatures up to 388°C, simulating common heavy-vehicle exhaust stream conditions. Although the TEG power output was significantly lower than the design value because of reduced heat transfer into the TE modules due to contact area mismatch and significant heat loss, many system performance parameters reached or even exceeded the target values at design conditions. Design modifications are being implemented to incorporate custom-designed TE modules into the system and to reduce the TE cold-side temperature to improve the TEG output.

EFFICIENCY OF GAS-FIRED HEAT GENERATORS FOR INDIVIDUAL AND DECENTRALIZED HEATING SYSTEMS

Modern equipment for heating systems of residential consumers, public buildings is characterized by a significant variety of design and efficiency. Gas-fired heat generators have several advantages when compared with devices on other types of fossil fuels. The main advantages of gas heat equipment are to reduce emissions into the environment, increase the efficiency. For consumers, an important aspect is the economic reduction of heating costs, the ability to control and regulate, the high security of modern systems using gas fuel. The safe use and high efficiency of gas heating equipment depends on a number of factors. The first, it is the use of gas fuel corresponding to the specified parameters. Secondly, it is the organization of the process of supplying air and removing combustion products for burning. Thirdly, it is the process of supplying gas with specified parameters, which is determined by the process of functioning of the gas distribution network. The article describes the work of gas heat generators at different temperatures of the incoming combustion air. Depending on the installation of the equipment, the air temperature for combustion may differ significantly from the temperature at which the heat generators were tested. Thus, the efficiency will differ from that stated in the passport when the temperature of the air entering the combustion changes. In the gas heat generators, there are a number of losses associated with chemical, mechanical incomplete burning, losses with products of combustion. In the work, all losses were analyzed, and the efficiency of a gas heat generator of 60 kW power was determined. As a result of the study, the annual effect in terms of gas volume was determined for given conditions.

Energy saving potential of a model-predicted frost prevention method for energy recovery ventilators

This study evaluates the energy-saving potential of a prediction model-based pre-heat coil operation method for frost prevention in energy recovery ventilators, compared to existing approaches. Energy recovery ventilator (ERV) requires pre-heating of the incoming outdoor air to prevent undesirable condensation and frost formation in the enthalpy exchanger during winter. Conventionally, the introduced outdoor air is pre-heated to a certain constant temperature using a pre-heat coil, resulting in unnecessary energy consumption. Maintaining a constant pre-heat temperature during the operation of the ERV is not ideal as the frost threshold temperature varies with the outdoor air temperature and humidity. Therefore, to reduce pre-heating energy consumption, a prediction model-based pre-heat coil operation method is proposed herein. A numerical model predicting the frost threshold temperature based on the outdoor air and exhaust air conditions was developed, and validated using the optimal Latin hypercube design method. Subsequently, a series of energy simulations was performed considering an identical residential model, located in 8 cities with different climatic conditions, to evaluate the energy-saving potential of the proposed pre-heat coil operation method compared to conventional methods. The proposed method consumed 7%–72% less energy in the ERV operation and required a 1%–21% smaller pre-heat coil capacity than the conventional method. Thus, the proposed operation method is superior to the conventional method as it prevents frost formation and consumes a minimal amount of energy.

The active external heat and mass transfer multifunctional “one-wall” model with “nullified” friction resistance parietal boundary layer for the high-speed aircraft

In this paper, a new “single-wall” scheme of a high-speed wingless jet aircraft without compressor, which has the smallest, practically “zeroed” external friction and heat and mass transfer resistance with an active external near-wall boundary layer and tangential injection of the superheated steam from a cooling jacket SCC walls was proposed. Moreover, due to the limited flow rate of the combustible laminar sublayer vapor injection and the laminar “scaly” sublayer zeroed friction, the average Mach number of the vortex external near-wall boundary layer will be only 2% less than the Mach number of the flight speed. This circumstance allows not to merge the frontier layer of the hull (“fuselage”), as is done on the overwhelming majority of the aircrafts, but to use the energy and mass of the near-wall boundary layer as a normal incoming air flow.

Early cases of SARS-CoV-2 infection in Uganda: epidemiology and lessons learned from risk-based testing approaches \u2013 March-April 2020

BackgroundOn March 13, 2020, Uganda instituted COVID-19 symptom screening at its international airport, isolation and SARS-CoV-2 testing for symptomatic persons, and mandatory 14-day quarantine and testing of persons traveling through or from high-risk countries. On March 21, 2020, Uganda reported its first SARS-CoV-2 infection in a symptomatic traveler from Dubai. By April 12, 2020, 54 cases and 1257 contacts were identified. We describe the epidemiological, clinical, and transmission characteristics of these cases.MethodsA confirmed case was laboratory-confirmed SARS-CoV-2 infection during March 21–April 12, 2020 in a resident of or traveler to Uganda. We reviewed case-person files and interviewed case-persons at isolation centers. We identified infected contacts from contact tracing records.ResultsMean case-person age was 35 (±16) years; 34 (63%) were male. Forty-five (83%) had recently traveled internationally (‘imported cases’), five (9.3%) were known contacts of travelers, and four (7.4%) were community cases. Of the 45 imported cases, only one (2.2%) was symptomatic at entry. Among all case-persons, 29 (54%) were symptomatic at testing and five (9.3%) were pre-symptomatic. Among the 34 (63%) case-persons who were ever symptomatic, all had mild disease: 16 (47%) had fever, 13 (38%) reported headache, and 10 (29%) reported cough. Fifteen (28%) case-persons had underlying conditions, including three persons with HIV. An average of 31 contacts (range, 4–130) were identified per case-person. Five (10%) case-persons, all symptomatic, infected one contact each.ConclusionThe first 54 case-persons with SARS-CoV-2 infection in Uganda primarily comprised incoming air travelers with asymptomatic or mild disease. Disease would likely not have been detected in these persons without the targeted testing interventions implemented in Uganda. Transmission was low among symptomatic persons and nonexistent from asymptomatic persons. Routine, systematic screening of travelers and at-risk persons, and thorough contact tracing will be needed for Uganda to maintain epidemic control.

(Invited) Development of Durable and Low Cost Membrane Humidifiers for Fuel Cell Systems

In order to operate effectively, currently commercialized fuel cell proton exchange membranes require sufficient hydration to ensure good proton transport. Hydration also ensures that membrane in the fuel cell stack will have a longer operational lifetime. In order to ensure adequate hydration in the stack, most liquid-cooled PEM fuel cell systems use external humidification. Without external humidification, the fuel cell must be operated at a lower operating temperature to ensure that the stack will not dry out. Operating the stack at lower temperature requires that the coolant loop in the system must reject a greater amount of heat, necessitating a large radiator, which increase system volume. Furthermore, operating at lower fuel cell stack temperatures leads to a significant trade-off in terms of stack power output and acceptable environmental operating ranges.Membrane humidifiers are an efficient form of external humidification that transport humidity through a membrane from the cathode exhaust to the incoming cathode supply air stream. In these humidifiers, membranes with a dense selective layer are used to transport water vapour without allowing oxygen and nitrogen to diffuse through the membrane. Since the membrane humidifier is coupled to the stack cathode exhaust and supply, in order to maintain its function, the membrane humidifier must not leak air or else reactant oxygen will bypass the stack through the humidifier. The humidifier must maintain a high level of water vapour transport and low air leakage over the lifetime of the device.In this presentation we present our work developing low-cost selective membranes for fuel cell humidification. These membranes are functional over a wide temperature range (-30 to +110°C) and have high water vapour permeance. They are resistant to contamination, relative humidity cycling, freeze-thaw cycling, oxidation, hydrolysis, and acidic conditions that are present in the cathode exhaust.This presentation will also discuss the incorporation of these flat-sheet membranes in to heat and mass exchangers (membrane humidifier cartridges). These cartridges are compact with a high membrane-to-volume ratio, high water vapour transport, and have low pressure loss. The membrane humidifiers are robust to a wide range of operating conditions. Furthermore, the design of these cartridges allows the humidifier to be manufactured at a low cost in high manufacturing volumes.Finally, this presentation will discuss membrane-based heat and mass exchanger performance at different operating conditions. A performance model will be presented which summarizes humidifier performance as a function of membrane properties, exchanger design and architecture, and fuel cell operating conditions.

Passively improving liquid sorbent based atmospheric water generation by integration of fuel cell waste products

Although interfacial atmospheric water generation is a new concept that can generate freshwater from renewable energy, its water generation rate is too low for widespread use. This paper proposes to integrate the fuel cell to a similar device but instead uses the electrochemically generated waste heat to drive the regeneration process of the liquid sorbent material. Furthermore, the electrochemically generated water is used to increase the relative humidity of the incoming air. Thus, by solely relying on the fuel cell waste products, water recovery rates that are theoretically higher than direct atmospheric water generation are achieved. A steady-state physics model based on the difference in water partial pressure to achieve water absorption and desorption is used to analyze the liquid sorbent device’s performance. Furthermore, the effect of various design parameters such as the salt mass fraction, the fuel cell operating power, the ambient relative humidity, etc. have been studied. Results demonstrate that up to 1.8 kg/h and 0.82 kg/(m2 h) of liquid water can be obtained by fuel cells with an operating temperature range that is consistent with the high-temperature proton exchange membrane fuel cell. This implementation would allow an FC waste heat utilization ratio of up to 0.8.

Assessment of the effect of humidity of air-cooled in the absorption refrigeration machine on the operation of an energy gas turbine

Due to the fact that the construction of combined cycle plants has become the main trend in the development of the world heat power industry in the last two decades studies of the operating modes and operation of such equipment are very relevant at the moment. The aim of this work is to study the effect of chilled air in an absorption refrigeration machine on the operation of a stationary gas turbine installation. The operation of a gas turbine installation is affected by the temperature of the surrounding air due to changes in its density and humidity at different temperatures and because of the different useful work of the gas turbine. The standard adopted in the design of gas turbines is 15 °C. An increase in ambient temperature leads to a decrease in the generated power of the gas turbine. The influence of gas turbine power from ambient air can be reduced by means of cooling units for incoming air (absorption refrigeration machine (ARM)), or by modernizing the gas flow part of gas turbines and injecting water or carbon dioxide. This study is devoted to the influence of humidity of air entering the gas turbine compressor from the ARM, where it was previously cooled. It was noted that air humidity affects the efficiency of the ARM and therefore the useful power of gas turbines. The power of a gas turbine can be increased to 7-9 MW when using the ARM.